Bring the pot to the boil with plenty of salted water. Add the lasagne sheets one by one and cook until soft for about 5 minutes. Pour into a bowl of cold water. In the meantime peel and chop the onion and garlic. Drain the tuna. Clean and quarter the mushrooms.
Heat the oil in a pan. Fry onion and garlic until transparent. Fry the mushrooms for about 2 minutes. Stir in tuna and season with salt and pepper. Add 50 g cream, bring to the boil and stir in 1 teaspoon of sauce thickener. Let it boil for a short time and put it aside. Bring white wine and 100 g cream to the boil. Season with salt, pepper and nutmeg. Stir in parsley and 2 teaspoons of sauce thickener and cook for 1 minute. Spread the tuna mixture on one narrow side of each lasagne sheet and roll it up tightly. Cut two rolls diagonally in half.
Bring white wine and 100 g cream to the boil. Season with salt, pepper and nutmeg. Stir in parsley and 2 teaspoons of sauce thickener and cook for 1 minute. Spread the tuna mixture on one narrow side of each lasagne sheet and roll it up tightly. Cut two rolls diagonally in half. Arrange the tuna rolls on two heat-resistant plates. Pour sauce over them and sprinkle with cheese. Bake in the preheated oven (electric range: 225 °C/ gas: level 4) for approx. 6 minutes. Wash, quarter and seed the tomatoes. Cut the flesh into cubes. Sprinkle tuna lasagne with diced tomatoes and garnish with parsley as desired
Arrange the tuna rolls on two heat-resistant plates. Pour sauce over them and sprinkle with cheese. Bake in the preheated oven (electric range: 225 °C/ gas: level 4) for approx. 6 minutes. Wash, quarter and seed the tomatoes. Cut the flesh into cubes. Sprinkle tuna lasagne with diced tomatoes and garnish with parsley as desired