Hamburguesas de hongo portobello con queso gouda y pesto
fresh portobello mushrooms • hamburger buns • Gouda cheese (about 200 grams) • pesto • spaghetti sauce • ketchup, to taste (optional) • mustard, to taste (optional) • mayonnaise, to taste (optional) • wheat germ, as needed (optional) • lettuce, as needed (optional) • tomato, as needed (optional) • onion rings, as needed (optional) •