1. Preheat the oven to 350°F.
2. In a saucepan, melt 100g of butter and cook the finely chopped onion for 2 minutes. Add the flour and mix. Pour in the milk, stirring constantly. Reduce heat to low and thicken, whisking. Cook for 5 minutes. Add salt, pepper, and grated nutmeg.

3. In a pan, cook the sliced onion in the remaining butter for 2 minutes.

4. Add the dill and salmon, reduce heat to low.

5. Add the bechamel sauce, mix. Heat for 4 minutes. Season with salt and pepper.

6. Fill each crepe with the fish mixture; fold the 4 edges.

7. Place the crepes on a baking sheet lined with parchment paper.

8. Bake for 10 minutes.

9. Remove from the oven and serve immediately.