Bring a large saucepan of water to the boil and add the spaghetti with a little salt. Cook to al dente, according to instructions, then remove from heat and drain, making sure to save some of the cooking water. In a separate pan, steam the asparagus, peas and broad beans for 2-3 minutes then dunk into cold water to prevent overcooking. Heat a little olive oil in a pan over a medium heat and add the pancetta. Fry until golden then add the shallot and garlic, stirring until everything begins to caramelise. In a bowl, blend the egg yolks, Parmesan, basil, mint, lemon zest and juice.