Ingredients

1/4 c. Mayonnaise
2 tbsp. Mustard (I used whole grain)
2 tbsp. Ketchup
1/2 tsp. Cayenne Pepper
2 tbsp. butter
1/2 whole Medium Onion, Finely Diced
8 oz. Mushrooms, sliced
4 dashes Worcestershire Sauce
Kosher salt and Freshly Ground Black Pepper
1 lb. Ground Beef
2 tbsp. Heavy Whipping Cream
2 dashes Worcestershire Sauce
1 tsp. Kosher Salt
Freshly Ground Black Pepper
2 slices Swiss Cheese, cut into four squares
4 slider buns
Kosher pickle, sliced

Instructions

Melt butter in a large skillet. Add onions and cook over medium heat for five minutes, stirring frequently. Add mushrooms, Worcestershire, salt and pepper. Cook for several minutes over medium heat, or until all liquid has evaporated. Transfer mushroom mixture to a separate bowl.

Mix ground beef, heavy cream, Worcestershire, and salt and pepper in a bowl. Form meat mixture into 4 or 5 patties. Make an indentation with your thumb to keep the patties from plumping too much when they cook.

In the same skillet as the one used to cook the mushrooms, heat to medium-high heat. Add four patties at a time, indented side face up. Cook for 3-4 minutes, then flip. Spoon generous portion of mushroom mixture on each patty, then top with two squares of Swiss. Place lid on skillet and cook for an additional 2 minutes, until burgers are cooked through, and cheese is melted.

To plate, spread sauce on both sides of buns and top with burger. Add pickle to top bun to fancy it up.