Melt the fat, add the flour, sweat briefly and remove the pan from the heat. Peel, wash and slice the carrots. Wash and clean the mangetouts. Wash and peel asparagus, cut off woody ends.
Cut the asparagus into approx. 4 cm long pieces. Peel and wash the potatoes, cut in half depending on size and cook in boiling salted water for about 20 minutes. Cook the asparagus in boiling salted water with a pinch of sugar for about 15 minutes.
After 8 minutes add carrots and after 12 minutes add peas and mangetout. In the meantime, boil the eggs in boiling water for about 10 minutes until hard, then rinse, peel and cut into slices. Pour vegetables into a sieve, collect vegetable stock and measure 500 ml.
Pour milk and vegetable stock into the roux while stirring, bring to the boil and season with salt, pepper and a little nutmeg. Add the vegetables to the sauce and carefully fold in the eggs. Arrange potatoes and egg ragout on plates.
Garnish with chervil.