Preheat grill or griddle. Spread 1 teaspoon of rosemary aioli on both sides of each piece of bread. Place 1 slice Gouda cheese on the base piece of bread. Top with sliced apples, followed by the remaining 2 slices of Gouda cheese and the top piece of bread.
Grill for 5 minutes, turning midway through, or until bread is toasted and cheese is melted. Serve immediately