1) Heat the oven to 210C/Gas 7.
2) Bring a medium saucepan of water to a boil over high heat, salt the water and cook the pasta to al dente, 7 minutes or so. Drain and quick-cool the pasta on a baking sheet.
3) While the pasta cooks, toast the pine nuts. Make a thick herb pesto by placing the herbs, cheese, garlic and nuts in a food processor with some salt and pepper. Turn the processor on and stream in about 5 tablespoons of olive oil - make the pesto very thick.
4) Place the meat in a bowl and season with salt and pepper. Add the cooked pasta, egg, breadcrumbs and half of the pesto to the meat. Mix to combine. Form into 16 balls and place on a parchment paper-lined baking sheet. Let the spaghetti pop out of the meatballs like porcupine quills. Coat the balls with a little olive oil and roast for 12 to 15 minutes until firm and golden in colour. Remove from the oven and place on a serving platter.
5) While the meat roasts, heat a healthy drizzle of olive oil in a saucepan over medium-high heat. Add the onions and carrots, season with salt and pepper, and saute for 5 minutes. Stir in the stock, add the tomatoes and crush them with the back of a wooden spoon. Cook for 5 minutes more, then stir in the remaining pesto.
Transfer the sauce to a serving bowl or four individual ramekins for dipping.