For the tomato sauce, fry the garlic clove crushed in a drizzle of olive oil. Add the tomato coulis, salt, pepper and simmer over low heat until it thickens.
For garnish, wash spinach and blanch it in boiling water for few minutes. Drain and let cool. Then with a knife, chop them finely. In a bowl, mix the chopped spinach, eggs, ricotta, grated parmesan, adding the pinch of nutmeg, salt and pepper.
For bechamel, cut the butter into cubes and melt on a low heat in a saucepan. Remove from heat, add the flour and stir quickly. Stir in the hot milk little by little, whisking, cook over low heat, stirring constantly. Add a pinch of nutmeg and salt.
Once the sauces are ready, preheat the oven to 200 °. Garnish the Cannelloni with the spinach-ricotta mixture.
In an oiled gratin dish, place the cannelloni on a thin layer of béchamel, cover with a layer of tomato sauce, and finish with béchamel. Sprinkle with grated parmesan cheese, add the diced Mozzarella and bake for 20 to 25 minutes.