Heat 1 tsp. melted butter in a large skillet over medium heat.

Add thinly sliced leek tops and season with salt (if desired).

Cover the skillet, reduce the heat to medium-low, and cook for 7 to 10 minutes, or until the leeks are tender.

Set the cooked leeks aside.

Brush 4 slices of country sourdough bread with half of the remaining melted butter.

Place the buttered bread slices butter-side down on a baking sheet.

Divide the grated provolone cheese among the bread slices.

Layer each slice with one-quarter of the cooked leek mixture and 1 red bell pepper half (if using).

Cover with the remaining bread slices.

Brush the sandwich tops with the remaining melted butter.

Heat a large skillet or griddle over medium-low heat.

Cook the sandwiches in the skillet for 4 minutes, or until browned and crisp.

Flip the sandwiches, and cook for 3 minutes more, or until the second side is browned.