Peel, wash and cut the carrots into pieces. Wash and peel the asparagus, cut off the woody end. Cut asparagus into pieces. Wash and halve sugar snap peas. Wash and clean spring onions and cut into diagonal rings.
Cook the carrots in plenty of salt water for about 6 minutes. Cook pasta in boiling salted water according to package instructions. Add asparagus to the carrots after 1-2 minutes. Add sugar snap peas 1-2 minutes before end of cooking.
In the meantime heat oil in a pan. Press the sausage meat as small balls out of the skin into the pan and fry for 3-4 minutes all around. Scoop the vegetables out of the water and rinse briefly in cold water.
Melt the fat in a pot. Stir in flour and sweat on at medium heat for 1-2 minutes. First add 500 ml vegetable stock, then milk while stirring and simmer for about 1 minute. Season the sauce with lemon juice, salt and pepper.
Drain the pasta. Add the vegetables, including the spring onions, and meatballs to the sauce and bring to the boil. Wash the chervil, dab dry and chop finely, except for 2 stems. Add chopped chervil to the vegetables.