Peel and wash the potatoes and cook them in boiling salted water for about 20 minutes. Boil eggs for about 8 minutes, rinse in cold water, peel and halve. Peel, wash and slice carrots.
Peel the kohlrabi, cut into six pieces and cut into slices. Wash the pods, dab dry and cut into strips. Steam carrots and kohlrabi in a pot covered with a little water for about 5 minutes until al dente.
Cook the sugar snap peas for 2-3 minutes. Season with salt, pepper and some sugar. Dice ham. Heat the oil in a larger pot. Brown the ham cubes briefly in it and take them out. Heat fat in hot frying oil.
Stir in the flour and sweat. Deglaze with cream, milk and stock, bring to the boil and simmer for 1-2 minutes while stirring. Remove the vegetables from the water and add them to the ragout with the eggs. Season to taste with salt, pepper, sugar and lemon juice.
Wash the herbs, dab dry and, except for some chervil for garnishing, pluck leaves from the stems. Chop the leaves finely and stir them into the sauce, except for a little bit for sprinkling. Drain the potatoes and arrange on plates with ragout, sprinkle with ham and chopped herbs and garnish with chervil.