St. Patty’s Melt Recipe

Peel the onion and cut it in half pole-to-pole. Slice each half into thin half-moons (about 1/8-inch thick).

Heat a 10-inch skillet over medium heat. Add vegetable oil and 1 tablespoon butter; when the butter has melted and begins to foam, add the sliced onions in an even layer.

Sprinkle the onions with 1/4 teaspoon kosher salt and 1/4 teaspoon sugar. Stir to coat, then cook, stirring every 2–3 minutes, until the onions are soft and beginning to brown, about 10–12 minutes.

Reduce heat to medium-low. Continue to cook, stirring every 3–5 minutes to prevent burning. If onions start to stick or look dry, add 1 tablespoon water to deglaze. Cook until deeply golden and caramelized, about 15–20 more minutes (total 25–32 minutes). Season with 1/8 teaspoon black pepper. Remove from heat and keep warm.

Prepare bread

Spread about 3/4 tablespoon butter evenly on one side of each rye bread slice. If using mustard, spread 1/2 teaspoon Dijon on the unbuttered side of one slice.

Assemble

Place one slice of rye, buttered side down, in a clean skillet or griddle over medium-low heat. Top with one slice Swiss cheese, then layer the warm caramelized onions evenly over the cheese. Add the optional thinly sliced corned beef or pastrami if using, then place the second slice of Swiss cheese on top. Finish with the other slice of rye, buttered side up.

Grill the sandwich

Cook the sandwich over medium-low heat for 3–4 minutes, checking that the bottom bread is deep golden and not burning. Press gently with a spatula, then carefully flip the sandwich and cook another 3–4 minutes until the other side is golden and the cheese is fully melted. If the bread is browning too quickly before cheese melts, lower the heat and cover the pan for 1–2 minutes to trap heat and encourage melting.

Finish & serve

Remove sandwich to a cutting board and let rest 1 minute. Slice in half on the diagonal. Serve immediately with optional pickle slices on the side.