Preheat panini press.
Stack your sandwiches. Between two pieces of bread, stack your cheese, prosciutto and mayonnaise. I stacked mayonnaise, 1 slice of cheese, prosciutto and then the next slice of cheese.
In a shallow bowl, beat milk, butter, and eggs. Dip both sides of each sandwich in the egg mixture and grill in the panini press for about 3 minutes or until it is crisp and golden to your likeness.
Cut sandwich in half, dust with powered sugar and serve each sandwich with 1 Tbsp of raspberry jam.