Wash and peel the asparagus. Do not cut the lower third of each asparagus spear into pieces. Wash lemon hot, grate dry, cut in half and cut 2 slices from 1 half. Bring 1 litre of water, 1 tsp salt and 2 tsp sugar to the boil. Add the asparagus pieces, peel and lemon slices and simmer for about 20 minutes
Cut the remaining asparagus spears into pieces. Rinse the mangetout, drain and cut diagonally into strips. Heat the oil in a pan. Fry the asparagus tips for 4-5 minutes while turning them. 1-2 minutes before the end of the cooking time, fold in the sugar snap peas and season with salt and pepper
Pour the asparagus stock through a sieve. Melt the fat in a pot. Dust with flour and sweat it on. Add cream and asparagus stock and bring to the boil while stirring. Season to taste with salt, pepper, a few dashes of lemon juice and sugar
Add fried asparagus mixture to the soup, arrange in soup bowls and garnish with chervil if desired