Mushroom-omelette roll Sienimunakas-kääryle

Ingredients
Omelette batter:
 * 6 eggs
 * 5 dl milk
 * 1 dl wheat flour
 * 1 tsp salt
 * 1/2 tsp white pepper

Filling:
 * 3 tbsp butter, margarine or cooking oil
 * 1 l chantarelles, hedgehog mushrooms, ceps
 * 2-3 onions, salt, black pepper
 * basil or thyme
 * a little cream or crème fraiche

On top:
 * grated cheese

Directions
Preheat the oven to 200° C. To prepare the batter, first mix the flour in the milk. Beat the eggs in a separate bowl and add to the flour and milk mixture. Spice with salt and white pepper. Line a high-edged baking plate with greaseproof paper and pour the omelette batter on the paper. Bake in the oven until light brown. Overturn the omelette on another piece of greaseproof paper and remove the paper from the bottom. Chop the onions for the filling. Fry the chopped mushrooms in hot oil, add the onions and let cook until the liquid has nearly evaporated. Spice with salt and pepper, and, if you like, basil or thyme. (In case you prefer the filling to be more saucelike, add a little cream to the mixture and let cook for a while). Check the taste. Spread the mixture on the omelette and roll the sheet up. Carefully move the roll on a greased ovenproof plate and sprinkle grated cheese on top. Heat the omelette roll in 200° C before serving