Shroomy Cheeseburger with Maple Thyme Caramelized Onions

Chef Kalisa Martin's current favorite cookbook is Cherry Bombe: The Cookbook (Clarkson Potter, 2017), a collection of recipes from women in the food world. She loves the Shroomy Cheeseburger. “We’ve all made burgers, but I never thought about grating mushrooms into them before,” says Martin.

Photography By Rebecca McAlpin | June 10, 2019

Ingredients

SERVINGS: Makes 4 burgers

Burgers

4 ounces button mushrooms, finely shredded
1 pound ground beef, 80⁄20 lean-to-fat ratio
Kosher salt

Caramelized Onions

4 tablespoons (1/2 stick) unsalted butter
2 large Vidalia onions, thinly sliced
3 tablespoons maple syrup
2 tablespoons balsamic vinegar
2 garlic cloves, minced
1 teaspoon kosher salt
1 teaspoon lemon zest
1 tablespoon fresh thyme, finely chopped
Kosher salt and freshly ground black pepper

Toppings

4 slices cheddar cheese
4 burger buns, toasted
3 tablespoons mayonnaise (optional)
1 tablespoon ketchup (optional)
4 butter lettuce leaves

Preparation

1. Make the burgers: In a medium bowl, mix the mushrooms, beef, and a pinch of salt until well combined. Refrigerate the mixture for about 1 hour.

2. Meanwhile, make the caramelized onions: Melt the butter in a large skillet over medium-high heat. Add the onions to the pan, turn the heat to medium-low, and cook, stirring frequently, for 20 minutes, until the onions are soft and translucent but not browned. Add the maple syrup, vinegar, garlic, salt, and some pepper to the pan. Cook for 20 to 30 minutes more, or until the onions are soft, brown, and caramelized. The slower you cook them and the lower the heat, the better. When done, turn off the heat and stir in the lemon zest and thyme. Taste and season with a pinch more salt if necessary.

3. Preheat the oven to 350°F.

4. Shape and cook the burgers: Remove the meat from the fridge and heat a cast iron skillet over medium-high heat. Form the meat into 4 equal patties. Sprinkle the top and bottom of each with a pinch of salt and some black pepper. Drop your burger patties into the hot ungreased pan.

5. Cook for 4 minutes. Once the burgers have a nice dark-brown crust, turn down the heat slightly, flip the burgers, and cook to your liking, 2 to 4 minutes more. Place a slice of cheese on top of each burger. Remove the burgers from the pan, set on a plate, and loosely cover with aluminum foil. Allow the burgers to rest for 4 minutes.

6. Meanwhile, in a small serving bowl, mix together the mayonnaise and ketchup. Smear the mixture on one side of each bun, top with a lettuce leaf then a burger, and finish with a big spoonful of onions.