Ingredients

3 tablespoons salted butter

2 yellow onions, thinly sliced

Kosher salt and black pepper

3/4 cup apple cider

1 tablespoon fresh thyme leaves

1 tablespoon chopped fresh sage

1 pinch crushed red pepper flakes

4 slices prosciutto (optional)

8 slices sourdough bread

2 tablespoons extra virgin olive oil

1 1/2 cups shredded fontina cheese

1 1/2 cups shredded gouda or white cheddar cheese

1 honeycrisp apple, thinly sliced

Instructions

Step 1: Melt 2 tablespoons of butter in a large skillet over medium-high heat. When the butter shimmers, add the sliced onions and cook for 3 minutes until softened. Pour in half of the apple cider, season with salt and pepper, and cook another 5 minutes until the cider has mostly evaporated.

Step 2: Add the remaining cider and continue cooking for 5 more minutes or until the onions are golden and caramelized. Stir in the thyme, sage, and crushed red pepper flakes, then cook for an additional minute. Remove the onions from heat.

Step 3: In a separate skillet over medium heat, cook the prosciutto slices until crisp, about 2 minutes per side. Remove and set aside.

Step 4: Brush the outside of each bread slice with olive oil. On the inside of half the slices, layer the fontina and gouda (or cheddar) cheeses, caramelized onions, apple slices, and prosciutto if using. Top with the remaining bread slices, olive oil side facing out.

Step 5: Place 1 to 2 sandwiches at a time in the skillet. Cook until golden brown on each side, about 3 to 5 minutes per side. During the last minute of cooking, add 1/2 tablespoon butter and 2 fresh sage leaves to the pan for extra flavor. Repeat with remaining sandwiches and serve immediately, topping with the crispy sage leaves.

Tips & Variations

For a vegetarian option, omit the prosciutto or substitute with sautéed mushrooms for additional umami flavor.

Use a combination of cheeses like Gruyère or mozzarella if fontina and gouda aren’t available.

If apple cider is not on hand, white grape juice or a dry white wine can add a similar sweetness to the onions.

Make sure to cook the onions slowly to develop deep caramelization for the best flavor.

FAQs

Can I make this sandwich vegan?

To make a vegan version, replace the butter with plant-based margarine, use vegan cheese alternatives, and skip the prosciutto. The onions and apples provide excellent flavor even without animal products.

What type of apple works best in this recipe?

A crisp, slightly tart apple like Honeycrisp or Granny Smith works well to balance the sweetness of the caramelized onions and richness of the cheese.