1Pre-heat oven to 190 Degrees C.
2In a large skillet, cook the onion in olive oil over moderate heat for 4-5 minutes.
3Add spinach and season with salt and pepper; sauté for 5 minutes. Remove from heat to cool down.
4Make the ricotta mixture: Combine ricotta, spinach and ¾ cup Parmesan cheese; season with salt and pepper.
5Prepare béchamel sauce: In a sauce pan melt butter and add flour, cook for 2-3 minutes.Add warm milk and bring to a simmer, whisk well so there are no clumps, season with salt and pepper. When the sauce comes up to a simmer, cook for an additional 5 minutes.
6Pan spray a 13” x 9” baking dish. On the first layer spread ½ cup béchamel sauce. Top with 4 Lasagne sheets, 1 cup ricotta mixture and a sprinkle of Parmesan cheese.
7Continue the same process for 3 more layers. For the top layer spread remaining béchamel and ricotta mixture, sprinkle with Parmesan cheese.
8Bake for 35-40 minutes or until golden brown and bubbly on top. Once cooked, let it rest for 5 minutes then slice, serve and enjoy!