1 Preheat your oven to 200 degrees.
2 Melt the butter in a pan, add the finely sliced leeks. Stir and place the lid on for the leeks to slowly steam and cook. Lower the heat and cook for 10 minutes, stirring every few minutes. Add the mustard and season with salt and pepper.
3 Line a small tray with baking parchment. Add the leeks to the centre of the tray. Scatter with some fresh dill. Lay the salmon darnes on top then season with salt and pepper. Pour over the white wine. Squeeze over a little lemon juice. Fold up the sides of the parchment into a tight parcel. You could also cook this in a lidded casserole dish.
4 Bake in the oven for 10-15 minutes, until the salmon is cooked through. Carefully open the paper as the hot steam will escape. Squeeze over some fresh lemon juice and scatter with freshly dill.
5 Divide the cooked orzo into four bowls then top with the buttered leeks and salmon.