Wash and clean the Swiss chard, eliminating any damaged leaves and the tougher stalks. Cook it in plenty of boiling, salted water for about 15 minutes; then strain and leave to cool. In the meanwhile, prepare the batter for the crepes: put the sifted flour, milk, eggs and a pinch of salt into a bowl, stirring well with a whisk in order to obtain a smooth batter without lumps; then leave to rest.
For the béchamel sauce: while you bring the milk to the boil, melt the butter over a very low heat in a small, heavy-bottomed saucepan. When it has melted, add the flour and stir them together for 2-3 minutes with a whisk, without letting the mixture brown. Pour the boiling milk into the saucepan a little at a time, stirring continuously. Cook for approximately 10 minutes, over a very low heat, taking care to not stop stirring so that the sauce doesn’t stick to the bottom of the pan. Turn the heat off and season with salt and nutmeg. Cover with cling film, placing it in contact with the surface of the béchamel so no “skin” forms.
Now prepare the crepes: heat 1 spoonful of olive oil in a heavy-bottomed frying pan, pour in a ladle of batter and spread it out over the bottom of the pan. Cook for a couple of minutes on one side, then turn it over and cook the other side. When the crepe is cooked, transfer it on to a plate and continue in the same way until you have finished the batter (after every 3-4 crepes, pour a spoonful of oil into the pan). Using a frying pan with a diameter of around 22 cm, you will get about 15 crepes.
Remove the skin from the sausage and coarsely crumble it into a frying pan, in which you have heated 1 spoonful of olive oil. Let it brown slightly all over, then remove from the heat.
Now it’s time for the tomato sauce: heat the clove of garlic with the oil in a heavy-bottomed saucepan. When it has begun to brown, remove it and add the peeled tomatoes (previously squashed in a dish with a fork) and chopped basil. Season with salt, stir and cook over a moderate heat for about 10 minutes.
Take the chard that you left to cool, squeeze it into balls and the chop it finely on a chopping board. Put it into a bowl with the ricotta, grated pecorino and sausage, and mix everything together thoroughly to combine all the ingredients. The filling for your crepes is now ready (for a meatless version, simply don’t use sausage).
Grease the bottom of a (large) oven dish with oil, spread 2 spoonfuls of tomato sauce and 2 spoonfuls of béchamel sauce in it. Fill each crepe with 2 heaped spoonfuls of the filling, roll them up and arrange them side by side in the oven dish. Cover with the rest of the béchamel and tomato sauce, sprinkle with the grated aged and fresh pecorino, and bake in a preheated oven, at 250 °C, for about 15 minutes... until the cheese has melted, and a tasty golden crust has formed on top. Before serving, leave your crepes to rest for about 10 minutes and then buon appetito!