Preheat the oven to 350 F (180 C).
Rub the gratin dish with the garlic clove, cut in half, until it’s used up, then brush it with a little olive oil. Set aside.

In a bowl, combine the flour, create a well and pour in the eggs, basil pesto, and olive oil in the center.
Mix gradually with a whisk, while adding the milk, to obtain a homogeneous batter.
Add pepper to taste and mix well.

Cut the bocconcini balls into slices and scatter them in the prepared gratin dish.
Pour the batter over them.
Dot with prosciutto slices, shaped into rosettes.
Bake for 40 to 45 minutes.
Serve with a green salad.