Clean, peel, halve and slice the kohlrabi. Wash and clean the mangetouts. Wash chervil, shake dry, except for something to garnish, pluck leaves from the stems and chop.
Whisk together the egg, milk and chervil. Season with salt and pepper. Layer kohlrabi and sugar snap peas alternately in a greased casserole dish (approx. 1 litre capacity). Spread egg milk on top and cook in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for about 30 minutes.
Remove from the oven, place the ham on top and garnish with chervil.