Slice your focaccia square in half horizontally. If it's been sitting around, warm it in the oven for about 3–4 minutes at 180°C so the outside crisps up.

Spread a tablespoon of pesto on the bottom slice.

Slice the mozzarella di bufala and lay it over the pesto.

Slice the tomatoes thickly, sprinkle with a little salt to draw out some moisture, then layer them on top. Tuck the basil leaves between the tomato slices. Spread the second tablespoon of pesto on the inside of the top slice, then close the sandwich.

Finish with a drizzle of olive oil, a pinch of salt, and a crack of pepper.