Peel, wash and halve the potatoes. Cover and cook in boiling salted water for about 20 minutes.
Peel and wash the carrots and kohlrabi. Cut carrots into slices, kohlrabi into large cubes. Steam vegetables in good 1⁄4 l boiling water with broth for 6-8 minutes. Drain vegetables, collect broth.
Wash the parsley, put a few leaves aside and chop the rest finely. Grate cheese. Heat the fat in a pot. Sweat flour in it. Stir in vegetable stock, milk and cream, bring to the boil. Simmer sauce for about 3 minutes.
Season to taste with salt and pepper. Melt half the cheese in the sauce and stir in chopped parsley.
Drain the potatoes. Spread with carrots, kohlrabi and sunflower seeds in a greased Aufl tin. Pour sauce over it and spread the rest of the cheese on top. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/gas: level 3) for about 30 minutes.
Garnish with the remaining parsley.