Enjoy St. Patrick’s Day flavors year-round with this hearty sandwich. Deli corned beef and sauerkraut are quick shortcuts for slow cooked corned beef and cabbage. Beer-braised, caramelized onions add another layer of flavor for a crispy sandwich that hits on all points.
Melt 1/2 tablespoon butter in a large skillet over medium-high heat. Add the onion and sprinkle with the sugar, 1/2 teaspoon salt, and pepper to taste. Cook, stirring occasionally, until soft and golden, about 10 minutes. Add the beer and continue cooking, stirring occasionally, until the onions are tender and the liquid is slightly syrupy, about 8 more minutes. Remove from the heat and stir in the corned beef, Worcestershire sauce and mustard.
Divide half of the cheese between 2 bread slices; top with the corned beef mixture, and the remaining cheese. Close the sandwiches with the remaining 2 bread slices.
Melt the remaining 1 tablespoon butter in a large skillet over medium heat. Add the sandwiches and cook, pressing occasionally with a spatula, until the bread is toasted and the cheese melts, about 4 minutes per side, adding more butter to the pan if needed.
Rinse the sauerkraut before you use it so the sandwich won’t taste too salty.