Then find a metal baking tray or ovenproof dish that will fit the cannelloni in one layer so it's nice and snug. Take your metal tray or a saucepan, put it on a high heat and add your butter, a drizzle of olive oil, one of the sliced garlic cloves, a handful of marjoram or oregano and the grated nutmeg. By the time the pan is hot the garlic should be soft. Put as much spinach as will fit into the pan. Keep turning it over; it will wilt quickly so you will be able to keep adding more spinach until it's all in.
After 5 minutes, put the spinach into a large bowl and leave to cool. Place the pan back on the heat, add a little olive oil, the other clove of sliced garlic, your basil stalks and the tomatoes, then fill one of the empty tomato tins with cold water and add this too. Bring to the boil, then turn the heat down, add a pinch of salt and pepper and the sugar, and simmer for about 10 minutes, until you get a loose tomato sauce consistency. Then take the pan off the heat and add the basil leaves.
By now the spinach will have cooled down, so squeeze any excess liquid out of it and pour this back into the bowl. Finely chop the spinach and put it back into the bowl. Mix it with the liquid, add the ricotta and a handful of the Parmesan, and then use a piping bag to squeeze the mixture into the cannelloni. You can make your own piping bag by getting a sandwich bag and putting the spinach mix into the corner of it. Then twist the bag up and cut the corner off. Carefully squeeze the filling into the cannelloni tubes so each one is filled right up.
Lay the cannelloni over the tomato sauce in the pan. Or you can pour the tomato sauce into your ovenproof dish and lay the cannelloni on top.
To make the white sauce, mix together the crème fraîche, anchovies and the 2 handfuls of Parmesan with a little salt and pepper, then loosen with a little water until you can spoon it over the cannelloni. Drizzle with olive oil, sprinkle with the remaining Parmesan and the mozzarella pieces, and bake for about 20 to 25 minutes until golden and bubbling.