2 tablespoons butter, at room temperature 3 slices prosciutto 2 slices sourdough bread Dijon mustard, to taste 1/2 cup shredded gruyere 1/2 honey crisp apple Handful of spinach Start by crisping the prosciutto. Place the prosciutto in a cold, dry, nonstick frying pan and turn the heat up to medium-high. Crisp, until the edges become lightly golden and curled; remove from the pan and set aside. The prosciutto will crisp up as it cools. Cut the apple in half and slice thinly.