Heat the fat, add the flour and sweat briefly. Remove the pot from the heat. Clean, peel, halve and slice the kohlrabi. Wash and clean the mangetouts. Prepare rice in boiling saffron-salted water according to package instructions.
Boil up the vegetable stock. Add kohlrabi and cook for about 8 minutes. After 5 minutes add mangetout and peas. Pour the vegetables into a sieve and collect the stock. Measure out 100 ml. Pour milk and vegetable stock into the roux while stirring.
Bring to the boil and simmer for about 3 minutes. Season to taste with salt, pepper and lemon juice. Add the vegetables to the sauce and warm them up briefly. Arrange the ragout on a plate. Garnish with chervil. Add rice.