Dice the onion and press the garlic. Halve the mushrooms and slice them. Heat the butter in a wide pan, sauté the onion, garlic and mushrooms over a medium heat for 10 minutes, season lightly with salt. Stir in the flour and deglaze with the wine. Stir in the cream, 100 ml water and stock cube. Simmer over a low heat for approx. 15 minutes, season with salt and pepper. Cook the lasagne sheets in salted water until al dente, then drain. Coarsely grate the Grana Padano, finely chop the chives. Arrange the lasagne sheets with the mushroom mixture and sprinkle with Grana Padano and chives.