original recipe from

Cheesy Truffle & Spinach Burgerswith Roasted Sweet Potatoes & Lemon-Caper Mayo

WWe're making a velvety sauce to complement simply seared prime beef burgers. First, we're tossing sharp white cheddar and our savory truffle zest together with a touch of cornstarch (which helps give the sauce it's thick, rich texture), then finishing it in the pan with a splash of cream until the mixture is melty and perfect for topping the burgers.

INGREDIENTS

Cook Time: 35 min
Servings: 3

24 oz Usda Prime Ground Beef
4 Challah Buns
5 oz Baby Spinach
1½ lbs Sweet Potatoes
1 Lemon
1 bunch Parsley
4 oz White Cheddar Cheese
½ tsp Truffle Zest Seasoning (Includes Natural Truffle Flavor And Black Summer Truffle)
½ cup Cream
1 Shallot
¼ tsp Crushed Red Pepper Flakes
1 Tbsp Capers
¼ cup Mayonnaise
¼ cup Cornstarch
1 Tbsp Verjus Blanc

DIRECTIONS

Prepare the ingredients 
Place an oven rack in the center of the oven; preheat to 450°F. Wash and dry the fresh produce. Cut the sweet potatoes into 1/2-inch rounds. Peel and thinly slice the shallot. Quarter and deseed the lemon. Grate the cheese on the large side of a box grater. In a bowl, combine the grated cheese, 2 teaspoons of cornstarch (you will have extra) and as much of the truffle zest as you'd like. Halve the buns. In a separate bowl, combine the mayonnaise, capers, and the juice of 2 lemon wedges; season with salt and pepper. Roughly chop the parsley leaves and stems.

Roast the sweet potatoes
Transfer the sweet potato rounds to a sheet pan. Drizzle with olive oil and season with salt and pepper. Toss to coat and arrange in an even layer. Roast 23 to 25 minutes, or until lightly browned and tender when pierced with a fork. Remove from the oven and evenly top with the juice of the remaining lemon wedges.

Cook the spinach
Meanwhile, in a large pan (nonstick, if you have one), heat 2 teaspoons of olive oil on medium-high until hot. Add the sliced shallot; season with salt and pepper. Cook, stirring occasionally, 1 to 2 minutes, or until softened. Add the spinach and as much of the red pepper flakes as you'd like, depending on how spicy you'd like the dish to be; season with salt and pepper. Cook, stirring frequently, 1 to 2 minutes, or until the spinach is wilted. Add the verjus (carefully, as the liquid may splatter). Cook, stirring constantly, 30 seconds to 1 minute, or until the liquid has cooked off. Transfer to a bowl and cover with foil to keep warm. Wipe out the pan.

Form & cook the patties
Place the beef in a bowl. Season with salt and pepper. Gently mix to incorporate. Form the mixture into four 1/2-inch-thick patties. In the same pan, heat a drizzle of olive oil on medium-high until hot. Add the patties. Cook 4 to 5 minutes per side, or until browned and cooked through.* Leaving any browned bits (or fond) in the pan, transfer to a work surface. Carefully drain off and discard any excess oil. *The USDA recommends a minimum safe cooking temperature of 160°F for beef.

Toast the buns
Working in batches, add the halved buns, cut side down, to the pan of reserved fond. Toast on medium-high 30 seconds to 1 minute, or until lightly browned. Transfer to a work surface. Wipe out the pan.

Make the cheese sauce & serve your dish 
Heat the same pan on medium until hot. Add the cream (carefully, as the liquid may splatter). Cook, whisking constantly, 30 seconds to 1 minute, or until simmering. Add the cheese mixture. Cook, whisking constantly, 1 to 2 minutes, or until the sauce is thickened and smooth. Turn off the heat. Assemble the burgers using the toasted buns, cooked patties, cheese sauce, and cooked spinach. Serve the burgers with the roasted sweet potatoes on the side. Top the sweet potatoes with the lemon-caper mayo and chopped parsley. Enjoy!

Thanks to Blue Apron for this amazing recipe

Original recipe link: Cheesy Truffle & Spinach Burgers with Roasted Sweet Potatoes & Lemon-Caper Mayo