For the ricotta white sauce: place the ricotta, grated cheese, milk and olive oil in a blender and blend until creamy. Add a little more milk if necessary. Season with sea salt, black pepper and a pinch of nutmeg
For the sauteed spinach: Heat the olive oil in a large skillet over medium-low heat. Fold in the shallot and spinach leaves, cover with a lid and let it cook for about 2 minutes. Remove the lid, stir and cook for 2 more minutes, then remove from the heat and set aside until needed.
Preheat oven to 180 and arrange a baking tray onto the middle rack.
Brush the bottom of a 6x8 inches baking dish with a layer of ricotta white sauce.
Then top with lasagna sheets, use a knife to cut them so it fits perfectly your baking dish.
Spread 1/2 of the pea pesto evenly over the lasagna noodles, and top with 1/2 the sliced potatoes, 1/2 the mozzarella and 1/2 the basil leaves.
Top with lasagna noodles then spread an even layer of ricotta cheese sauce over the pasta. Top with the sauteed spinach leaves.
Then, top again with lasagna sheets, and spread the remaining pea pesto over the pasta. Arrange the remaining sliced potatoes, mozzarella and basil leaves on top.
Finally, arrange another layer of pasta noodles on top, and spread the remaining white sauce all over the noodles, to make a thick white layer.
Note that the ricotta white sauce tends to be a little drier than classic bechamel sauce, so be generous when you spread it all over the top.
Bake the lasagna in the oven for about 20 minutes, or until the pasta is cooked through and the top is gently bubbling.
For some nice golden spots over the top, place it under the grill for about 5 more minutes.
Remove the baking dish from the oven and serve.