Baked Blueberry French Toast Casserole

Name: Baked Blueberry French Toast Casserole
Prep time: 30 min
Cook time: 1 h 10 min
Total time: 1 h 40 min
Yield: 8 servings
Cuisine: American
Ingredients: 1 lb loaf (450 g) brioche loaf, cut into 1-inch (2.5 cm) cubes, crusts left on (about 10–12 cups); 1 tablespoon (14 g) unsalted butter, softened, for greasing the dish; 2 cups (300 g) blueberries, fresh, or frozen and not thawed; 8 large (400 g) large eggs, at room temperature; 2 cups (480 ml) whole milk; 1 cup (240 ml) heavy cream; ½ cup (100 g) granulated sugar; ¼ cup (60 ml) pure maple syrup; 1 tablespoon (15 ml) pure vanilla extract; 2 teaspoons (5 g) ground cinnamon; ¼ teaspoon (½ g) ground nutmeg (optional); 1 teaspoon (2 g) lemon zest, finely grated (optional); ½ teaspoon (3 g) fine sea salt; ½ cup (62 g) all-purpose flour; ⅓ cup (70 g) light brown sugar, packed; ½ teaspoon (1 g) ground cinnamon; ⅛ teaspoon (0.7 g) fine sea salt; 4 tablespoons (57 g) unsalted butter, cold, cut into ½-inch (1 cm) cubes; 2 tablespoons (15 g) powdered sugar, for dusting (optional); ½ cup (120 ml) pure maple syrup, warmed (optional)

From the MyKitchenBank Kitchen

Cubes of buttery brioche soak overnight in a cinnamon-vanilla custard with juicy blueberries, then bake into a puffed, golden casserole with a crisp brown sugar streusel. Assemble the night before and just bake in the morning.

Prep: 30 min
Cook: 1 hr 10 min
Wait: 8 hr 40 min
Total: 10 hr 20 min
Makes: 1 (9×13-inch) casserole, 8 generous servings

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Ingredients

8 servings

For the casserole
1 lb loaf (450 g) brioche loaf, cut into 1-inch (2.5 cm) cubes, crusts left on (about 10–12 cups)
1 tablespoon (14 g) unsalted butter, softened, for greasing the dish
2 cups (300 g) blueberries, fresh, or frozen and not thawed
8 large (400 g) large eggs, at room temperature
2 cups (480 ml) whole milk
1 cup (240 ml) heavy cream
½ cup (100 g) granulated sugar
¼ cup (60 ml) pure maple syrup
1 tablespoon (15 ml) pure vanilla extract
2 teaspoons (5 g) ground cinnamon
¼ teaspoon (0.5 g) ground nutmeg (optional)
1 teaspoon (2 g) lemon zest, finely grated (optional)
½ teaspoon (3 g) fine sea salt
For the streusel topping
½ cup (62 g) all-purpose flour
⅓ cup (70 g) light brown sugar, packed
½ teaspoon (1 g) ground cinnamon
⅛ teaspoon (0.7 g) fine sea salt
4 tablespoons (57 g) unsalted butter, cold, cut into ½-inch (1 cm) cubes
To serve
2 tablespoons (15 g) powdered sugar, for dusting (optional)
½ cup (120 ml) pure maple syrup, warmed (optional)

Equipment (7)

9×13-inch (23×33 cm) baking dish, about 3 inches (7.5 cm) deep
2 large rimmed baking sheets
Large mixing bowl (at least 5 quarts / 5 L)
Large whisk and a medium bowl for the custard
Aluminum foil
Instant-read thermometer
Serrated knife and cutting board

Steps

Before you start

Plan ahead: the casserole needs at least 4 hours (ideally 8 hours or overnight) to soak, plus 30 minutes on the counter before baking.
Use a day-old or lightly dried brioche loaf (about 1 lb / 450 g). Fresh, soft bread turns mushy; the drying step in the recipe fixes this.
If using frozen blueberries, do not thaw them. Thawed berries bleed and turn the custard gray-purple.
Cut the streusel butter into cubes and keep it in the fridge until you need it.

1
Dry the breadOven 300°F / 150°C
- Heat the oven to 300°F (150°C).
- Spread the brioche cubes in a single layer over two rimmed baking sheets.
- Bake for 12–15 minutes, stirring once halfway, until the cubes feel dry and slightly firm on the outside but are still pale.
- Let them cool on the pans while you continue.
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Ready when: Cubes feel dry and firm to the touch, pale golden at most, not browned
Tip: Don't toast them brown. You want dry, not crunchy, so they can still soak up the custard.
2
Grease the dish
- Rub the softened butter over the bottom and sides of a 9×13-inch (23×33 cm) baking dish, covering every corner so the casserole releases cleanly when served.
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Ready when: Dish has an even, glossy film of butter with no bare spots
3
Whisk the custard
- In a large bowl, whisk the eggs, granulated sugar, maple syrup, vanilla, cinnamon, nutmeg (if using), lemon zest (if using) and salt for about 1 minute until the sugar dissolves and no streaks of egg white remain.
- Whisk in the milk and cream until fully combined and slightly frothy.
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Ready when: Custard is uniformly pale yellow with no visible egg white streaks
Tip: Room-temperature eggs blend more smoothly into the milk and cream.
4
Assemble the casserole
- Spread half of the dried bread cubes in the prepared dish and scatter 1 cup (150 g) of the blueberries over them.
- Add the remaining bread, then slowly pour the custard evenly over the top.
- Press the bread down firmly with a spatula so all the cubes are touching the custard.
- Scatter the remaining 1 cup (150 g) blueberries over the top and gently press them in.
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Ready when: Custard comes about three-quarters of the way up the bread, with the top cubes slightly damp
Tip: If using frozen berries, keep them frozen until the moment they go in the dish.
5
Cover and chill
- Cover the dish tightly with plastic wrap or foil and refrigerate for at least 4 hours, ideally 8 hours or overnight.
- Press the top cubes down once after about 1 hour if you are around, so they soak evenly.
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Ready when: Nearly all the custard has been absorbed, with only a little pooling at the bottom
6
Make the streusel
- In a medium bowl, stir together the flour, brown sugar, cinnamon and salt.
- Add the cold butter cubes and rub them into the dry ingredients with your fingertips until the mixture forms pea-sized clumps with some crumbly bits.
- Refrigerate until the oven is ready.
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Ready when: Mixture holds together when squeezed and breaks into pea-sized clumps
Tip: Keep the butter cold so the streusel bakes up crisp, not greasy.
7
Rest and preheatOven 350°F / 175°C
- Take the dish from the fridge 30 minutes before baking and leave it on the counter, still covered.
- Meanwhile, heat the oven to 350°F (175°C) with a rack in the center.
- Right before baking, sprinkle the streusel evenly over the top, then cover the dish loosely with foil.
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Ready when: Dish no longer feels icy on the bottom; oven at full temperature
Tip: Putting a cold glass dish straight into a hot oven risks cracking it. Let it warm up first.
8
Bake coveredOven 350°F / 175°C
- Place the foil-covered dish on a baking sheet (to catch any drips) in the 350°F (175°C) oven and bake for 40 minutes.
- The casserole will puff and the custard will begin to set.
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Ready when: Casserole is puffed, and the edges are set and bubbling slightly
Tip: Tent the foil so it doesn't touch the streusel and pull it off.
9
Bake uncoveredOven 350°F / 175°C
- Remove the foil and bake for 15 more minutes, until the streusel is deep golden and the center no longer jiggles when you nudge the dish.
- Insert an instant-read thermometer into the center; it should read 165°F (74°C).
- A knife in the center should come out with no liquid egg, only blueberry juice.
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Ready when: Streusel is deep golden, center is puffed and set, and registers 165°F (74°C)
Tip: If the streusel browns too fast before the center reaches 165°F, re-cover loosely with foil and bake a few minutes longer.
10
Rest and serve
- Let the casserole rest on a wire rack for 10 minutes so the custard firms up for clean slices.
- Dust with powdered sugar if using, cut into 8 portions, and serve warm with warmed maple syrup.
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Ready when: Casserole holds its shape when cut, with no liquid pooling in the cut edges
Tip: Dust with powdered sugar just before serving; it dissolves into the top if added early.

Good to know

Tips

Press the bread down after pouring in the custard so every cube is saturated, since dry pockets bake up tough.
Don't skip the rest on the counter, as a very cold dish extends baking time and can leave the center underdone.
Check the center with a thermometer rather than relying on color; the top browns well before the middle sets.
Add the lemon zest if your berries are mild, as it brightens the whole dish.

Make ahead

"Assemble the casserole through step 4, cover tightly, and refrigerate up to 24 hours. Keep the streusel in a separate covered container in the fridge and sprinkle it on just before baking. Bake from step 7 onward."

Storage & reheating

"Room temperature: up to 2 hours after baking. Fridge: cover tightly and keep up to 4 days. Freezer: wrap cooled portions individually and freeze up to 2 months. Reheat: warm portions in a 325°F (160°C) oven for 12–15 minutes (from frozen, 25 minutes, covered with foil), or microwave a single portion for 60–90 seconds."

Substitutions

brioche loaf → challah, or thick-cut day-old white bread. Challah works almost identically. Plain white sandwich bread is softer, so dry it a few minutes longer.
heavy cream → additional whole milk (1 cup / 240 ml). The casserole will be a little less rich but still set well.
blueberries → raspberries, chopped strawberries or sliced peaches. Use the same weight (300 g). Keep frozen fruit frozen.
pure maple syrup → honey or light brown sugar (3 tablespoons / 40 g). Honey is sweeter, so use slightly less if you prefer.