Mushroom Walnut Burgers

Name: Mushroom Walnut Burgers
Prep time: 24 min
Cook time: 34 min
Total time: 58 min
Yield: 4 servings
Cuisine: American
Ingredients: ¾ cup (85 g) raw walnut halves; 12 oz (340 g) cremini mushrooms, wiped clean, stems trimmed, quartered; 1 tablespoon (15 ml) olive oil, for sautéing; 1 medium (about 5 oz) (150 g) yellow onion, finely diced (¼-inch pieces); 3 cloves (10 g) garlic cloves, minced; 1 tablespoon (16 g) tomato paste; 1 teaspoon (2½ g) smoked paprika; 1 teaspoon (1 g) dried thyme; 1 tablespoon (15 ml) soy sauce; 1 cup (175 g) cooked short-grain or medium-grain brown rice, cooled completely to room temperature or chilled; ½ cup (30 g) panko breadcrumbs; 1 large (50 g) large egg, lightly beaten; ½ teaspoon (3 g) fine salt; ¼ teaspoon (½ g) black pepper, freshly ground; 3 tablespoons (45 ml) olive oil, for pan-frying; 4 buns (280 g) hamburger buns, split; 4 tablespoons (56 g) mayonnaise (optional); 1 medium (150 g) ripe tomato, sliced into 4 rounds (optional); 4 leaves (30 g) butter lettuce leaves, washed and dried (optional)

From the MyKitchenBank Kitchen

Savory, meaty veggie burgers made with deeply browned cremini mushrooms, toasty walnuts, and sticky brown rice. They hold together, pan-fry to a crisp golden crust, and taste rich and umami-packed thanks to soy sauce and tomato paste.

Prep: 24 min
Cook: 34 min
Wait: 40 min
Total: 1 hr 38 min
Makes: 4 burgers

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Ingredients

4 servings

For the patties
¾ cup (85 g) raw walnut halves
12 oz (340 g) cremini mushrooms, wiped clean, stems trimmed, quartered
1 tablespoon (15 ml) olive oil, for sautéing
1 medium (about 5 oz) (150 g) yellow onion, finely diced (¼-inch pieces)
3 cloves (10 g) garlic cloves, minced
1 tablespoon (16 g) tomato paste
1 teaspoon (2.5 g) smoked paprika
1 teaspoon (1 g) dried thyme
1 tablespoon (15 ml) soy sauce
1 cup (175 g) cooked short-grain or medium-grain brown rice, cooled completely to room temperature or chilled
½ cup (30 g) panko breadcrumbs
1 large (50 g) large egg, lightly beaten
½ teaspoon (3 g) fine salt
¼ teaspoon (0.5 g) black pepper, freshly ground
For cooking and serving
3 tablespoons (45 ml) olive oil, for pan-frying
4 buns (280 g) hamburger buns, split
4 tablespoons (56 g) mayonnaise (optional)
1 medium (150 g) ripe tomato, sliced into 4 rounds (optional)
4 leaves (30 g) butter lettuce leaves, washed and dried (optional)

Equipment (8)

Rimmed baking sheet
Food processor
12-inch (30 cm) skillet (nonstick or cast iron)
Large mixing bowl
Rubber spatula
Plate or parchment-lined baking sheet for chilling patties
Wide metal spatula
Instant-read thermometer

Steps

Before you start

Use brown rice that is fully cooked and completely cooled (day-old is ideal). Warm or freshly cooked rice makes the mixture gummy.
Plan on 30 minutes of chilling before frying. Chilled patties hold together far better.
Have a 12-inch (30 cm) skillet ready. Nonstick or well-seasoned cast iron both work well.
Preheat the oven to 350°F (175°C) before you start so the walnuts can toast right away.

1
Toast the walnutsOven 350°F / 175°C
- Heat the oven to 350°F (175°C).
- Spread the walnuts on a rimmed baking sheet in a single layer and toast for 8 minutes, shaking the pan once halfway.
- Transfer them to a plate to cool.
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Ready when: Walnuts smell nutty and are lightly golden under the skins.
Tip: Walnuts burn quickly and turn bitter. Set a timer and pull them as soon as they smell toasty.
2
Chop walnuts and mushrooms
- Pulse the cooled walnuts in a food processor in 1-second bursts, 6 to 8 times, until they resemble coarse crumbs with some pea-sized pieces.
- Transfer to a large bowl.
- Add the quartered mushrooms to the processor (no need to wash it) and pulse 8 to 10 times until finely chopped into roughly ⅛- to ¼-inch pieces.
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Ready when: Mushrooms look like coarse ground meat, not a paste.
Tip: Work in two batches if your processor is small. Overcrowding turns the mushrooms to mush.
3
Brown the mushrooms
- Heat the 1 tablespoon sautéing olive oil in the 12-inch skillet over medium-high heat until shimmering.
- Add the chopped mushrooms and stir every minute or so for 10 to 12 minutes.
- They will first release liquid, then the liquid will cook off and the mushrooms will start to sizzle and brown.
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Ready when: The pan is dry, the mushrooms are deep golden brown, and they have shrunk to about half their volume.
Tip: Do not salt the mushrooms at this stage. Salt draws out more water and delays browning.
4
Add aromatics and seasoning
- Reduce the heat to medium.
- Add the diced onion and cook, stirring, for 3 minutes until softened.
- Stir in the garlic, tomato paste, smoked paprika, and thyme and cook 1 minute more.
- Pour in the soy sauce and stir for 30 seconds until it is absorbed and the pan is dry again.
- Remove from the heat.
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Ready when: Onion is translucent, the tomato paste has darkened slightly, and there is no liquid left in the pan.
Tip: Stir constantly once the tomato paste goes in so it caramelizes rather than scorches.
5
Cool the mixture
- Scrape the mushroom mixture into the large bowl with the walnuts and spread it out slightly.
- Let it cool for 10 minutes, stirring once or twice, so the hot filling doesn't scramble the egg or soften the rice.
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Ready when: The mixture feels barely warm to the touch.
6
Mix the burger base
- Add the cooked rice, panko, beaten egg, salt, and pepper to the bowl.
- Mix firmly with a spatula or your hands for about 1 minute, pressing and mashing some of the rice against the bowl so the mixture turns sticky and cohesive.
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Ready when: A handful squeezed in your fist holds its shape without crumbling apart.
Tip: If the mixture feels wet and loose, add 1 to 2 more tablespoons of panko. If it's crumbly, mash a bit more rice into it.
7
Shape the patties
- Divide the mixture into 4 equal portions (about 5 oz / 140 g each).
- With damp hands, pack each tightly and press into a patty about 3½ inches (9 cm) wide and ¾ inch (2 cm) thick.
- Place on a parchment-lined plate or baking sheet.
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Ready when: Patties have smooth edges with no cracks.
Tip: Pack firmly. Loosely formed patties crack and fall apart in the pan.
8
Chill the patties
- Cover the patties loosely and refrigerate for at least 30 minutes, or up to 24 hours.
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Ready when: Patties feel firm when pressed gently.
9
Pan-fry the burgers
- Heat 2 tablespoons of the frying oil in the 12-inch skillet over medium heat for 1 minute.
- Add the patties and cook undisturbed for 4 to 5 minutes until the bottoms are deep golden brown and crisp.
- Add the remaining 1 tablespoon oil around the patties, then flip carefully with a wide metal spatula and cook 4 to 5 minutes more.
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Ready when: Both sides are deeply browned and crisp, and the center reaches 160°F (71°C) on an instant-read thermometer.
Tip: Resist moving or pressing the patties while the crust forms. Flip only when they release easily from the pan.
10
Toast buns and assemble
- Wipe out the skillet and toast the buns cut-side down over medium heat for 1 to 2 minutes until golden.
- Spread mayonnaise on both halves, then layer lettuce, a burger, and a tomato slice on each bun.
- Serve right away.
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Ready when: Cut sides of the buns are golden and lightly crisp.
Tip: Let the burgers rest 2 minutes before assembling so the crust stays crisp and the interior sets.

Good to know

Tips

Cook the mushrooms until the pan is completely dry and they are well browned. Leftover moisture is the main cause of soft, crumbly burgers.
Use sticky short- or medium-grain brown rice if you can; it acts as the binder.
Chilling is not optional. It firms the patties so they don't break when flipped.
Use a thermometer to confirm 160°F (71°C) in the center, since the browned crust can look done before the middle is hot.

Make ahead

Shape the patties up to 24 hours ahead and refrigerate them covered on a parchment-lined plate. Or freeze shaped, uncooked patties (see storage) and fry from frozen.

Storage & reheating

Cooked patties keep in an airtight container in the fridge for up to 4 days. Reheat in a skillet over medium heat for 3 to 4 minutes per side, or in a 375°F (190°C) oven for 12 to 15 minutes. Freeze uncooked or cooked patties, separated by parchment, for up to 3 months; cook uncooked frozen patties over medium-low heat for 6 to 7 minutes per side, covered for the first 5 minutes, until the center reaches 160°F (71°C). Do not leave cooked burgers at room temperature for more than 2 hours.

Substitutions

large egg → 1 tablespoon ground flaxseed mixed with 3 tablespoons water, rested 5 minutes. Makes the patties vegan if you also use vegan buns and mayo. Patties will be slightly more delicate, so chill them the full 30 minutes.
raw walnut halves → Raw pecans, same weight. Gives a slightly sweeter flavor. Toast them the same way.
panko breadcrumbs → Rolled oats or gluten-free breadcrumbs, same amount. Use certified gluten-free oats or crumbs, plus tamari for the soy sauce and gluten-free buns, for a gluten-free burger.
cremini mushrooms → White button mushrooms, same weight. Button mushrooms have a milder flavor; the cooking time stays the same.