1. Bring plenty of salted water to a boil.
2. Cook the pasta sheets according to the package instructions until they bend.
3. Dip into cold water and lay on a kitchen towel to dry.
4. Heat 15 ml butter in a pan and fry the onion and garlic over a medium heat until soft.
5. Add the spinach and cook until it wilts.
6. Stir in the creme fraiche and season with salt, ground pepper and nutmeg.
7. Butter an ovenproof dish.
8. Lay some spinach and a salmon strip on each pasta sheet and roll up to resemble cannelloni.
9. Lay in the dish with the join underneath.
10. Heat the oven to 200C (180C fan) 400F, gas 6.
11. Melt the remaining butter.
12. Stir in the flour and fry until golden brown, then gradually stir in the milk with a balloon whisk.
13. Bring to a boil briefly, stirring continuously.
14. Season with salt, ground pepper and nutmeg.
15. Pour the sauce over the pasta rolls and sprinkle with cheese.
16. Bake for 20-25 minutes until the salmon is done and the pasta rolls are lightly browned.