Peel and chop the first onion and fry in 2 tablespoons of olive oil. Add tomatoes and creme fraiche and reduce to a thick consistency. Peel and chop the second onion, process the garlic, basil, spinach and the Parmesan cheese into a dough in the food processor, season with salt, sugar and pepper.
Fill the cannelloni with this mass (put in a freezer bag and cut off a corner, I put the cannelloni in a shot glass, then you don`t need 4 hands to fill it).
Grease a baking dish and place the cannelloni side by side. Pour the tomato sauce over it and top with the diced mozzarella and the butter flakes.