To make the mayo. In a small bowl or jar, whisk together all of the garlic pesto mayo ingredients. Season with salt and pepper.
Preheat the oven to 400°F.
Place the focaccia halves, cut side up, on a baking sheet. Spread the pesto mayo evenly over both halves. Layer the tomatoes, 6 slices of Muenster cheese, turkey, and crispy prosciutto over the bottom half of the focaccia. Arrange the remaining cheese slices on the top half.
Bake for 15 minutes, or until the cheese is melted.
Remove from the oven and layer the greens over the prosciutto. Place the top half of the focaccia over the greens and gently press down. Rub with olive oil. Return to the oven for 5 minutes, until the bread is toasted and crisp.
Slice into 6 pieces. Enjoy warm or chilled.
