Poil the potatoes. Quarter cabbage, remove stalk and cut into 3 cm squares. Bring salted water to the boil and add cappage leaves for 1 minute. Pour off water (reserve 500 ml), refresh with cold water and squeeze cabbage.
Heat butter and sautée flour, stir in reserved water and bring to the boil. Stir in creme fraiche and let all simmer for 15 minutes. Cool down and fold in eggs and the half of cheese. Season to taste with salt and pepper. Cover a casserole with butter and preheat oven to 180 °C. Peel potatoes and cut them into 1 cm slices of thickness. Cut mushrooms into slices. Dice onion and bacon, heat oil and sautée them lightly. Add potatoes and then mushrooms. Spice with salt, pepper and crushed garlic. Mix well potatoes and cabbage with the sauce, season to taste and place all into a casserole. Sprinkle with cheese and bake for about 40 minutes.