Clean, wash and drain the carrots, celery and leek. Dice vegetables finely. Peel onion and garlic, also finely dice onion, chop garlic.
Heat the oil in a large pan and fry the minced meat until crumbly. Finally add onions, garlic and vegetables, fry briefly and season with salt and pepper. Stir in tomato paste and deglaze with bouillon.
Coarsely chop the tomatoes in the tin with a long knife. Wash oregano, dab dry and chop, except for a little to garnish. Add tomatoes and oregano to the pan, bring to the boil and simmer covered over a low to medium heat for 15-20 minutes.
Meanwhile, put the spaghetti in plenty of boiling salted water and cook for 9-10 minutes until it bubbles. Pour onto a sieve, rinse briefly under cold water and drain. Slice the Parmesan very finely.
Season bolognese with salt and pepper and arrange on plates with spaghetti. Sprinkle with parmesan slices and serve garnished with fresh olives and oregano.