In a small fry pan on medium heat, add the prosciutto and cook until crispy, about 4-5 minutes. Place on a plate with napkins to absorb any grease.

Mix the mayo with with the pesto sauce seasoning and stir well. Spread a generous layer over a single slice of bread.

On the plain slice of bread, layer the mozzarella, prosciutto, and tomato slices, then top with the slice with the pesto mayo.

Heat a grill pan or large fry pan on medium medium-high and brush with olive oil. Grill the sandwich for about 4-5 minutes on each side, or until prominent, brown grill marks appear on the bread.