Wash, peel, and chop the vegetables. Put them into a ceramic baking pan, sprinkle with salt and pepper, fresh basil leaves, then drizzle with olive oil.
Bake in a preheated oven at 200° C/392° C for 30 minutes. After baking, purée with a blender to the desired consistency.
For the sandwich:
Spread the basil pesto over the bread, place sliced mozzarella on top, and spread a little butter on the outside of the bread. Heat in a pan for 2 minutes on each side.