1 1/2 pounds ground beef chuck
About 1/4 cup Worcestershire sauce
3 tablespoons grated onion
Coarse salt and pepper
1 tablespoon vegetable oil
4 deli slices (not too thin) Emmentaler cheese
3 tablespoons butter
1 pound white mushrooms, slices
1 shallot, finely chopped
1/3 cup dry sherry
1 cup sour cream
1/4-1/3 cup buttermilk
1/4 cup dill, parsley, chives and thyme, finely chopped
1 tablespoon fresh lemon juice
1 teaspoon hot sauce
1 clove garlic, grated
4 brioche or other soft rolls, split
Pre-heat a cast iron skillet or griddle pan over medium-high heat. Combine the chuck, Worcestershire sauce, onion, salt and lots of pepper. Form into four patties (thinner at the center and thicker at the edges for even cooking). Add the oil to the hot pan; add the patties and cook, turning once, for 8-10 minutes for medium-rare to medium. Top the patties with the cheese, folded to fit the burgers, during the last 2 minutes of cooking.
Meanwhile, in a separate skillet, melt the butter over medium heat. Add the mushrooms and cook until browned, about 12 minutes. Add the shallot, season with salt and pepper and cook for 2-3 minutes more. Deglaze the pan with the sherry and remove from the heat.
In a bowl, stir together the sour cream, buttermilk, herbs, lemon juice, hot sauce and garlic; season with salt and pepper.
Put the cheeseburgers on the roll bottoms and top with the mushrooms. Slather the roll tops with the dressing and set into place.