Mix flour, mineral water, eggs and salt and let it swell for about 30 minutes. Soak porcini mushrooms in 1/4 litre of cold water. Clean, wash and cut the cabbage into eighths and cut out the stalk.
Cut cabbage into strips. Scald tomatoes, cut out stem base. Skin tomatoes and cut into slices. Heat 1 tablespoon of oil in a pan. Sauté the savoy cabbage in it. Add mushrooms with the liquid.
Cover and stew for about 15 minutes. Steam tomatoes for the last 5 minutes. For the sauce, bring the stock and milk to the boil and melt the cheese in it. Season sauce with salt and pepper. Wash the herbs.
Put something aside for garnishing. Cut the rest finely and fold into the sauce. Keep the sauce warm. Grease a coated pan with oil, heat up and add 1/4 of the crépe dough and bake until golden brown.
Warm up and bake 3 more crépes from the remaining dough. Fill with savoy cabbage and serve with sauce and remaining herbs.