Make a homemade pesto using my recipe or use a store-bought one.
Bring a pot of boiling salted water to the boil. Blanch the haricot verts for 2 mins and then remove and place into an ice bath to stop cooking. Dry them well.
Drain the mozzarella and place in a bowl along with the pesto, tomatoes, haricot verts, and olive oil. Season with salt and pepper to taste and drizzle with olive oil.
Serve at room temperature alongside some crusty bread.