Beef Patty Melt with Pimento Cheese

10 ounces ground sirloin
6 ounces ground beef short ribs
Kosher salt and cracked black pepper to taste
1/4 cup vegetable oil
2 Spanish onions, thinly sliced
8 slices (1/2 inch thick) rye bread, buttered on one side

HOMEMADE PIMENTO CHEESE
8 ounces sharp cheddar, coarsely shredded
1/2 cup mayonnaise
1/2 cup finely chopped Vidalia onion
3-1/2 ounces jarred pimentos, drained and diced
1 garlic clove, grated
Dash of hot sauce

Prepare the homemade pimento cheese:  Blend the cheddar, mayonnaise, onion, pimentos, garlic and hot sauce in a food processor until well combined.  Transfer the pimento cheese to a glass jar or bowl and refrigerate until firm, at least 1 hour.  Makes 1-3/4 cups.

Prepare the burgers:  Blend the ground sirloin and ground short ribs and sprinkle with salt and pepper.  Loosely form the meat into 4 equal 4-ounce patties about 1/2 inch thick.  Create a small well in the center of each patty, using your thumb.

Heat 2 tablespoons of the oil in a small saute pan over medium heat.  Cook the onions, sprinkling with salt and stirring occasionally, until caramelized, brown and soft, 25 to 30 minutes.

Season beef patties with salt and pepper to taste.  Heat a large cast-iron skillet or griddle pan over high heat and add 1 to 2 tablespoons of the oil.  Cook the burgers, well side up first, until browned on both sides, 3 to 4 minutes per side.  Transfer to a plate.

Spread the homemade pimento cheese on the non-buttered side of each slice of bread.  Top half of the bread slices with a pile of onions, then add the burger patties and top with the remaining bread slices.

Place the sandwich on the griddle and toast until the bread is golden brown and he cheese is beginning to melt, 2 minutes per side.

Serves 4.