Cheese Puff Sliders

Preheat oven to 450 degrees F (235 degrees C). Line a baking sheet with a silicone baking mat. Toss Gruyere and Cheddar cheeses together in a small bowl; set aside.

In a saucepan, combine water, butter, and salt. Bring to a simmer over medium heat. Reduce heat to low and add flour, stirring vigorously with a wooden spoon until a smooth, paste-like dough forms (2-3 minutes). Continue to cook, scraping the bottom of the pan, for another minute to lightly dry the dough. Transfer the dough to a bowl and let cool slightly (5-10 minutes).

Incorporate 1 egg, cayenne, and black pepper into the cooled dough, stirring until fully combined. The mixture may appear to separate initially, but continue stirring until smooth. Add the remaining egg and repeat. Gently fold in half of the cheese mixture.

Using a small scoop, portion 12 equal balls of dough onto the prepared baking sheet. Top each with the remaining cheese.

Place the baking sheet in the preheated oven and immediately reduce the temperature to 375 degrees F (190 degrees C). Bake until the puffs are golden brown and well-risen (30-35 minutes). Cool on the pan for a few minutes, then transfer to a wire rack to cool completely (10 minutes).

For the secret sauce, whisk together mayonnaise, ketchup, and mustard in a small bowl.

Divide the ground beef into 12 equal portions (2 ounces each). Gently press each portion into a 1/4-inch thick patty. Season both sides generously with salt and pepper. Heat a skillet over medium-high heat. Cook the patties, undisturbed, until a rich crust forms on the bottom (2-3 minutes). Flip and cook until the meat is cooked to your liking (2-3 minutes for medium-rare), allowing the juices to start to appear on top. Let the patties rest for a couple of minutes before assembling the sliders.

Slice the cheese puffs in half horizontally, like buns. Spread each half with a generous tablespoon of secret sauce. Add a burger patty, pickle slices, tomato slices, and lettuce (if using). Serve immediately and enjoy!