There are numerous versions of this classic recipe. Personally, I like the variation with two sauces, in which bechamel is used in the filling and tomato sauce is poured all around - it makes for a very colorful and attractive presentation. 

If you love creamy sauces, then use bechamel by itself; if you're a big fan of tomato sauce or you're cutting calories, cover the cannelloni with just tomato sauce. In the latter case, add a drizzle of cream when you gratinée the dish - the cream will help balance the acidity of the tomato.

1. Cook the onions in butter or oil until lightly colored; add the roughly torn spinach leaves, removing the stems and central vein if the leaves are large; when the leaves wilt, season with salt, pepper and nutmeg. Cook over low heat for about 10 minutes. 
2. Let cool, then mix in the eggs and ricotta. 
3. Meanwhile, cook the pasta in lightly salted boiling water - cook until tender, not just "al dente"!
4. Drain and cool until cool enough to handle.  Using scissors, cut the noodles in half widthwise. Place on a work surface. 
5. Place a line of filling onto each piece of pasta. Roll up and place in a baking dish. Repeat the process for all of the cannelloni. Cover with bechamel sauce; sprinkle with grated cheese and gratiné lightly before serving.
6. If you're using tomato sauce, sprinkle with marjoram, drizzle on the cream and gratinée lightly before serving.