Tostone Veggie Burgers with Mayo-Ketchup Sauce
Crisp, garlicky twice-fried green plantain tostones stand in for the bun, holding a smoky black bean patty, fresh lettuce and tomato, and a tangy Puerto Rican-style mayo-ketchup sauce. Naturally gluten-free if you swap the panko, and wonderfully crunchy on the outside, tender within.
- Prep
- 35 min
- Cook
- 25 min
- Wait
- 15 min
- Total
- 1 hr 15 min
- Makes
- 4 burgers (8 tostone buns, plus 1 extra tostone for snacking)
Steps
Before you start
- Choose plantains that are fully green and very firm. Yellow or spotted ones are sweeter and will not crisp or hold together as buns.
- Drain and rinse the black beans, then let them sit in a colander so they are as dry as possible. Wet beans make soft patties.
- Set a wire rack over a baking sheet and line a second plate with paper towels. You will need both for draining and keeping food warm.
- Have everything for assembly sliced and ready before you fry the tostones. They are best eaten hot and crisp.
Make the sauce
- In a small bowl, stir together the mayonnaise, ketchup, grated garlic, lime juice, and hot sauce if using, until completely smooth and an even pale pink.
- Cover and refrigerate while you work so the garlic mellows into the sauce.
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Ready when: Sauce is uniform in color with no streaks of ketchup.
Tip: Taste and add a little more lime juice if you like it tangier.
Mix the patty base
- Put the drained black beans in a medium bowl and mash with a potato masher or fork until about two-thirds are broken down, leaving some whole beans for texture.
- Add the panko, red onion, patty garlic, cilantro, beaten egg, cumin, smoked paprika, and ½ teaspoon salt.
- Stir firmly for about 1 minute.
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Ready when: Mixture is thick and sticky and holds together when pressed into a ball.
Tip: If it feels wet and loose, add 1 more tablespoon of panko.
Shape and chill patties
- Divide the mixture into 4 equal portions of about 100 g (3½ oz) each.
- With damp hands, press each into a patty about 3½ inches (9 cm) wide and ¾ inch (2 cm) thick.
- Place on a plate lined with parchment and refrigerate for 15 minutes so they firm up.
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Ready when: Patties feel firm and hold their shape when lifted.
Tip: Use this chill time to start peeling the plantains in the next step.
Peel and cut plantains
- Trim both ends of each plantain.
- Cut a shallow slit lengthwise through the skin along one ridge, without cutting deep into the flesh.
- Pry the peel off with your thumb and the tip of a knife, working in strips.
- Cut each plantain crosswise into three 1½-inch (4 cm) pieces.
- In a small bowl, stir the minced garlic and 1 teaspoon salt into the warm water until the salt dissolves.
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Ready when: Peeled pieces are pale yellow-white with no green skin clinging.
Tip: Green plantain peel is stubborn. Use a knife tip, not just your fingers, and cut off any stubborn bits.
Pan-fry the pattiesOven 200°F / 95°C
- Preheat the oven to 200°F (95°C) and set the wire rack on a baking sheet.
- Heat the patty oil in the 10-inch nonstick skillet over medium heat for 2 minutes until it shimmers.
- Add the chilled patties and cook undisturbed for 4 minutes, then flip carefully and cook 4 minutes more.
- Transfer to the rack in the oven to keep warm.
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Ready when: Both sides are deep golden brown and crisp, and the center reads 160°F (71°C) on an instant-read thermometer.
Tip: Don't press down on the patties as they cook, or they will crack and dry out.
First fry the plantainsOven 325°F / 165°C
- Pour the frying oil into the 12-inch skillet, which should be about ½ inch (1.25 cm) deep.
- Heat over medium heat to 325°F (163°C).
- Carefully add as many plantain pieces as fit without touching, usually 5 at a time.
- Fry for 3 minutes per side, turning with tongs or a slotted spatula.
- Move to a paper towel-lined plate.
- Keep the oil in the pan.
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Ready when: Pieces are pale golden with slightly softened edges and a fork pierces them easily.
Tip: Don't let them brown deeply now. That comes after smashing, and over-browning makes them tough.
Smash the tostones
- While the pieces are still warm, place one on a sheet of parchment, cover with a second sheet, and press straight down with a flat-bottomed glass until the piece is about ⅜ inch (1 cm) thick and 3½ to 4 inches (9 to 10 cm) wide.
- Repeat with all pieces.
- If the edges crack, gently press them back together with your fingers.
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Ready when: Each disc is an even, flat round with ragged but intact edges.
Tip: If a piece resists smashing or crumbles, it was undercooked. Return it to the oil for 1 more minute first.
Dip in garlic water
- Dip each smashed disc into the garlic-salt water for about 5 seconds, then lift out.
- Lay on a clean paper towel and pat the surfaces very dry, pressing gently.
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Ready when: Discs feel damp, not dripping, with no pooled water on top.
Tip: Wet plantains make the hot oil spatter violently. Pat each one thoroughly dry before it goes in.
Second fry until crispOven 350°F / 175°C
- Bring the oil back to 350°F (175°C) over medium-high heat.
- Fry the discs in 2 batches, 2 to 3 minutes per side.
- Lift to the wire rack and immediately sprinkle with the flaky salt.
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Ready when: Tostones are deep golden brown, crisp at the edges, and sound hollow when tapped.
Tip: Salt right away while the surface is still glistening so it sticks.
Assemble and serve
- Pick the 8 best tostones.
- Spread a generous spoonful of the sauce on 4 of them.
- Top each with a lettuce leaf, a tomato slice, a warm bean patty, and avocado if using.
- Add more sauce, then crown with a second tostone.
- Serve right away while the buns are crisp.
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Ready when: Burgers stand upright and the tostones are still crisp on the outside.
Tip: Press down gently. The tostones can crack if you squeeze too hard, so eat these with both hands.
Good to know
Tips
- Don't skip the second fry. It turns the soft, par-cooked plantain into a crisp, sturdy bun.
- Use a thermometer for the oil. Too cool and the tostones soak up grease; too hot and they brown before the center is tender.
- Keep the buns on the thinner side (⅜ inch) so they stay crisp and are easy to bite through.
- Make the sauce a few hours ahead for deeper garlic flavor, and serve extra on the side for dipping the leftover tostone.
Make ahead
"The sauce keeps 3 days in the fridge. Patties can be shaped up to 1 day ahead and refrigerated on parchment. Plantains can be first-fried and smashed up to 2 hours ahead; hold at room temperature, then dip and second-fry just before serving."
Storage & reheating
Best eaten right away. Store components separately: cooked patties and sauce in airtight containers in the fridge up to 3 days; tostones are best fresh and soften within hours. Freeze cooked patties up to 2 months. Reheat patties in a 350°F (175°C) oven for 10 to 12 minutes, and re-crisp tostones in a 400°F (200°C) oven or air fryer for 4 to 5 minutes.
Substitutions
- panko breadcrumbs → gluten-free breadcrumbs or crushed corn tortilla chips. Makes the patties gluten-free. Chips add extra corn flavor.
- large egg → 2 tablespoons ground flaxseed mixed with 3 tablespoons water, rested 5 minutes. Makes the patties vegan if you also use vegan mayo. Handle gently, as they are slightly more delicate.
- canned black beans → canned red kidney beans or pinto beans, drained. Use the same weight. Pinto beans give a softer, creamier patty.
- mayonnaise → vegan mayonnaise. Works equally well with the ketchup and lime.