For the tempura dough, mix 300 g flour, 1 teaspoon salt and baking powder in a bowl. Add mineral water and mix to a smooth dough. Put the dough aside
Bring salted water to the boil in a large pot. Cook the lasagne sheets in 2 portions for about 12 minutes. Keep finished lasagne plates warm. Melt 20 g butter in a small pot. Deglaze with vegetable stock and white wine. Bring sauce to the boil and simmer for about 5 minutes. Gradually stir 80 g butter into the sauce. Finally stir in sour cream and season to taste with salt, pepper and lime juice. Keep sauce warm
Peel and finely chop the onion. Heat 10 g butter and fry the onion cubes in it until translucent. Add peas and fry for about 3 minutes. Season to taste with salt, pepper and sugar. Keep peas warm
Heat the oil to approx. 175 °C. Wash salmon, dab dry, cut into strips and turn in 100 g flour. Dip portion by portion into the Tempura dough, drain and deep-fry for approx. 3 minutes. Let the fried salmon drip off on kitchen paper. Cut lasagne sheets in half. Arrange 3 lasagne plates, salmon, peas and sauce on plates