In a small skillet, warm sautéed mushrooms over low heat.
Form 6 balls of ground beef, press into patties, sprinkle with truffle salt and black pepper. Refrigerate until ready.
Bring a medium skillet up to medium-low heat. Cook burger patties for about 3 minutes. Add two Swiss cheese slices to each patty. Cover skillet with a lid, and cook for about 3 minutes more, or until cheese is melted, and burgers are cooked through.
Add a dollop of aioli to the bottom bun.
Add a spoonful of warmed sautéed mushrooms on top of the aioli.
Using a spatula, add a burger patty with melted cheese to the bottom bun. Add the top bun to fully assemble the sliders.
Plate and serve immediately with a side of aioli for dipping.