Slow Cooker Sourdough Caramelized Onion and Gruyère Savory Bread Pudding

Name: Slow Cooker Sourdough Caramelized Onion and Gruyère Savory Bread Pudding
Prep time: 15 min
Cook time: 3 h 30 min
Total time: 3 h 45 min
Yield: 6 servings
Cuisine: French
Ingredients: 6 eggs (300 g) large eggs; 1½ cups (360 ml) heavy cream; ½ cup (120 ml) whole milk; 2 tablespoons (30 ml) Dijon mustard; 2 teaspoons (2 g) fresh thyme, leaves only; ½ teaspoon (3 g) kosher salt; ¼ teaspoon (½ g) black pepper, freshly ground; 0.06 teaspoon (0.1 g) freshly grated nutmeg; 5½ cups (280 g) sourdough bread, cut into 1-inch cubes, lightly dried; 1½ cups (350 g) caramelized onions; 1½ cups (170 g) Gruyère cheese, finely grated; 1 tablespoon (14 g) unsalted butter, softened, softened, for greasing

From the MyKitchenBank Kitchen

A French-inspired savory bread pudding with tender sourdough, deeply caramelized onions, and melted Gruyère cheese, cooked low and slow until the custardy center is just set. Perfect as a side dish or light main course, and easily assembled ahead.

Prep: 15 min
Cook: 3 hr 30 min
Wait: 7 min
Total: 3 hr 52 min
Makes: 6–8 servings

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Steps

Before you start

If caramelizing fresh onions, do so 45 minutes ahead (or prepare the day before)
Cut sourdough bread into 1-inch cubes and let them sit uncovered for 2–4 hours (or overnight) to dry out slightly
Use a 6-quart slow cooker; a smaller one will overflow
Have all ingredients measured and ready before beginning

1
Butter the slow cooker
- Butter the inside of a 6-quart slow cooker generously, paying special attention to the corners and sides where the pudding can catch and stick.
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Tip: A well-buttered cooker prevents sticking and makes serving cleaner.
2
Spread bread base
- Spread half of the sourdough bread cubes (about 2.75 cups) evenly across the bottom of the prepared slow cooker, filling in gaps as much as possible.
3
Layer onions and cheese
- Over the bread layer, scatter half of the caramelized onions (about 0.75 cup) in an even layer, then sprinkle half of the grated Gruyère cheese (about 0.75 cup) evenly over the onions.
4
Mix the egg custard
- In a medium mixing bowl, whisk together the 6 eggs, 1.5 cups heavy cream, 0.5 cup whole milk, 2 tablespoons Dijon mustard, 2 teaspoons fresh thyme leaves, 0.5 teaspoon salt, 0.25 teaspoon black pepper, and a small grating of nutmeg (about 1/16 teaspoon).
- Whisk until completely smooth with no visible egg white streaks, about 1 minute.
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Ready when: Mixture is pale, uniform, and smooth with no streaks or lumps
Tip: Don't overmix or add air; you want a dense, smooth custard, not a foamy one.
5
First custard pour
- Pour half of the whisked egg mixture (about 1 cup) over the onion-cheese layer.
- Using a rubber spatula, gently press down on the bread to help it absorb the liquid, but do not mash or compress it heavily.
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Tip: Gentle pressing ensures even distribution; aggressive mashing creates a dense, compact pudding.
6
Add final layers
- Add the remaining bread cubes (about 2.75 cups) in an even layer, then scatter the remaining caramelized onions (about 0.75 cup) and finally the remaining Gruyère (about 0.75 cup) on top.
7
Final custard pour and soak
- Pour the remaining egg custard (about 1 cup) evenly over the top layer.
- Let the pudding sit uncovered for 2 minutes to allow the bread to begin absorbing the liquid; this prevents a dry top layer.
8
Cook on low heatOven 160°F / 70°C
- Cover the slow cooker with its lid and cook on LOW for 3.5 to 4 hours.
- The pudding is done when the edges are set and lightly browned, the center is mostly set but still has a slight jiggle (like panna cotta), and a knife inserted in the center comes out clean or with just a few moist crumbs.
- The internal temperature of the eggs should reach 160°F (71°C).
- Do not overcook, or the eggs will become tough and release excess liquid.
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Ready when: Center is set but slightly jiggly; knife comes out clean or with moist crumbs; internal temperature reads 160°F (71°C)
Tip: Slow cookers vary in heat. If yours runs hot, check at 3 hours. If it runs cool, you may need up to 4.5 hours.
9
Rest before serving
- Turn off the slow cooker and let the pudding rest, uncovered, for 5 minutes.
- This allows the structure to set and makes it easier to portion.
- Scoop portions into serving bowls or plates with a wide spoon and serve warm.
- Optionally garnish with a small sprig of fresh thyme.
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Tip: If the pudding seems too loose after resting, it was slightly undercooked; if very stiff and dry, it was overcooked—add a splash of warm cream when reheating next time.

Good to know

Tips

If caramelizing fresh onions, do so the day before and refrigerate; this develops their deep sweetness and saves active cooking time on serving day.
Drying out the bread cubes (2–4 hours uncovered or overnight) is essential: moist bread falls apart in the slow cooker, while properly dried bread holds its shape and absorbs custard evenly.
Slow cookers cook with gentle, even heat, so eggs stay creamy and custard-like—overcooking will make them tough and cause them to release excess liquid.
For a browned top, transfer the finished pudding to a buttered baking dish and broil on high for 2–3 minutes until golden, watching carefully to avoid burning.

Make ahead

Yes. Assemble the pudding completely, cover tightly, and refrigerate up to 12 hours before cooking. Add 15–20 minutes to the cooking time if starting from cold.

Storage & reheating

Room temperature: Store leftovers in an airtight container for up to 2 hours. Refrigerator: Cover and refrigerate for up to 4 days; reheat gently in a 325°F (160°C) oven for 10–15 minutes or in a skillet over low heat, stirring occasionally. Freezer: Not recommended, as the texture becomes grainy and weepy when thawed.

Substitutions

Gruyère cheese → Swiss cheese or sharp Cheddar. Use the same amount; Swiss is milder and creamier, sharp Cheddar adds more bite and tang.
sourdough bread → brioche or challah. Works beautifully but the pudding will be less tangy and slightly sweeter.
heavy cream → half-and-half. Use the same amount; the pudding will be slightly less rich but still creamy and delicious.
Dijon mustard → whole grain mustard or omit entirely. Whole grain adds subtle texture and mustard flavor; omitting gives a more classic, neutral flavor.