Clean the spinach of the stems and chop it. Heat the olive oil and saute it for 1-2 min. until softened.
Take the container off the heat. Let it cool and add the crumbled feta cheese. Stir until homogeneous.
Submerge the lasagna sheets briefly in a bowl with hot water.
Pour cream into the bottom of an oven dish, arrange a layer of sheets, put some filling on top. Pour on cream and continue in this order until out of ingredients, finishing off with a layer of sheets.
Pour cream over the lasagna, arrange round pieces of mozzarella on top.
Bake in a preheated oven to a golden crisp.