Wash potatoes thoroughly and cook in boiling water for about 20 minutes. In the meantime peel, wash and slice the kohlrabis. Peel and wash carrots, cut them in half lengthwise and cut them into large pieces. Cut off the lower woody ends of the asparagus. Wash the asparagus, cut into pieces
For the sauce, melt butter in a saucepan, dust with flour, sauté and gradually add stock and cream, stirring constantly. Bring to the boil while stirring, stir in 3/4 of the cheese. Season to taste with salt, pepper and sugar. Drain potatoes, quench briefly, remove skin. Cut potatoes into slices
Wash parsley, shake dry and pluck off all but a few leaves. Wash the meat, dab dry. Wrap 2 slices of bacon around each fillet, wrapping 2-3 parsley leaves in each. Heat oil in a pan. Fry the meat for 12-15 minutes, turning it over. Remove from the pan, season with salt and pepper, let rest for about 5 minutes
Meanwhile, put carrots and kohlrabi in boiling salted water and cook for 8-10 minutes. Add the asparagus about 2 minutes before the end of the cooking time. Pour vegetables into a sieve and drain well. Place the vegetables and potatoes in an ovenproof dish, leaving a small depression in the middle. Spread the sauce evenly over the vegetables, except for 4-5 tablespoons. Sprinkle with remaining cheese
Cook the casserole in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for approx. 25 minutes. Cut meat into coarse slices. About 10 minutes before the end of the baking time, place the meat in the depression on the vegetables and drizzle the rest of the sauce over it
Meanwhile wash the rocket, shake dry and chop finely. Chop parsley finely as well. Wash the lemon thoroughly, grate dry and finely grate the peel. Put olive oil, rocket, parsley and lemon peel in a tall mixing bowl. Season with salt and pepper. Briefly puree with a hand blender
Take the casserole out of the oven, sprinkle with a little parsley roughening oil. Garnish with rocket as desired. Add the remaining oil