2 large Russet potatoes
Extra virgin olive oil (EVOO), for the pans
4 slices bacon, cut into 1/2-inch pieces
Salt and freshly ground pepper
1 cup sour cream
2 tablespoons fresh chives, chopped
2 tablespoons fresh dill, chopped
1 clove garlic, finely grated or pasted
2 tablespoons prepared horseradish
4 tablespoons flat leaf parsley, chopped, divided
A splash of half-and-half or whole milk
2 pounds 80-percent ground beef (if you grind your own, use 1/2-pound each skirt steak, brisket and sirloin)
About 3 tablespoons Worcestershire sauce
2 teaspoons dry mustard
1 teaspoon cayenne pepper or 2 teaspoons hot sauce
1 small white or yellow onion, very thinly sliced
1/2 cup Irish stout, such as Guinness
1/2 pound sliced Cotswold or extra-sharp yellow cheddar cheese
Brioche or potato rolls, lightly toasted
Bread-and-butter pickles, for topping
Watercress, for topping
Peel the potatoes, then slice into thin wedges or cut into 3/4-inch dice. Heat a skillet over medium-high heat and add a drizzle of EVOO. Add the bacon and cook until crisp, then drain on a paper towel-lined plate. Add the potatoes to the fat in the skillet and season with a little salt and lots of pepper. Cook until browned, 5-6 minutes. Cover with foil and cook for 5 minutes. Remove the foil and cook until crisp, 7-8 more minutes.
Mix the sour cream, chives, dill, garlic, horseradish, 2 tablespoons parsley and half-and-half or milk in a small bowl. Season with salt and pepper.
Mix the beef, Worcestershire sauce, dry mustard cayenne or hot sauce and the remaining 2 tablespoons parsley in a large bowl. Sprinkle with salt and lots of pepper.
Heat a cast iron skillet or griddle over medium-high heat. Brush with oil, then add the beef mixture in four loose balls of equal size (do not shape them with your hands). Flatten with a spatula into 3/4-inch-thick patties. Scatter the onion slices over the top and press in with the spatula. Cook for 3 minutes, then flip and press the onion into the patties. Cook for 2 more minutes. Douse the pan with the beer and lay the cheese over the patties. Cover and cook until the cheese melts, about 1 minute.
Serve the burgers on the rolls with pickles and watercress.