Preheat your oven to 200C /180C fan / gas mark 6 / 400F.
Place a large colander in the sink. Put the spinach in the colander and pour over enough boiling water to wilt the spinach. Leave to drain and cool.
Next, gently fry the sliced garlic in a tablespoon of olive oil for a minute or two. Do not allow the garlic to colour. Tip in the 2 tins of tomatoes and bring the sauce to the boil. Turn off the heat and leave.
Next make the cheese sauce. Melt the butter in a medium sized pan on a low heat. When the butter is foaming, add the flour and stir until it’s mixed in. Then keep cooking for 2 minutes, stirring frequently.
Very gradually add the milk, stirring constantly. Make sure each bit of milk is incorporated before you add the next bit. If you do this slowly on a very low heat, you should end up with a smooth sauce with no lumps. However, if it does go wrong for any reason, you can always use a whisk to beat out the lumps.
When all the milk is incorporated, turn off the heat and add the parmesan, nutmeg, salt and pepper.
The spinach should now be cool enough to handle. Squeeze the spinach in your hands to get as much of the water out as you can, roughly chop it and then tip the spinach into a bowl.
Add the ricotta, basil, lemon zest and lemon juice to the spinach and mix together. Season with salt and pepper to taste.
To assemble the cannelloni: pour half the tomato sauce into a large ovenproof dish (big enough to fit 12 cannelloni tubes on one level.) Fill each cannelloni tube with about 2 tablespoons of mixture, using a teaspoon or piping bag. Arrange the tubes in the dish. Pour over the remaining tomato sauce and then the cheese sauce, ensuring all the cannelloni tubes are well covered with sauce.
Bake for 20 minutes until golden and bubbling. Serve with a side salad and some garlic bread too, if you fancy.
Notes
If you can't get hold of cannelloni tubes, use fresh lasagne sheets instead. Fill each lasagne sheet with about 2 tablespoons of mixture and roll into tubes. Arrange the tubes in the dish, seam side down, then continue with the recipe as written.
Suitable for freezing.
Nutrition information is approximate and meant as a guideline only.