Puree the cream with milk, feta and 1 tablespoon sour cream with a hand blender to make a sauce and season with salt, pepper and chili powder.
Cut the mushrooms into slices, fry them with the onions and garlic and season with salt and pepper. Add a dash of white wine and 1 tablespoon of sour cream, bring to the boil briefly and set aside.
Cook the spinach leaves in a little salted water and drain well.
In a medium-sized lasagna dish (suitable for 2 lasagna plates next to each other), first cover the bottom with a little feta sauce. Then place 2 sheets of lasagne on top. Layer a little spinach and mushrooms on top, and again some feta sauce. Place 2 more lasagne sheets on top. Then again layer in the spinach and feta sauce, again 2 lasagne plates, on top of the remaining mushrooms and the rest of the feta sauce. Finally, distribute the mozzarella slices on the casserole and dust with paprika powder.