The easiest is to buy ready sliced salmon - either cold smoked or gravad. This is a Swedish word meaning "to bury" the fish. This is the old method of curing for preservation where pieces of fish (or meat) were rubbed in with salt, sugar and salpeter and was then buried in the ground. Not sure if this particular method is still followed, when curing, but that's what it is. Cold smoked has a similar texture. Personally I prefer hot smoked, which is not very spread outside Scandinavia, at least I have trouble finding it in the UK and it was nowhere to be found in Germany. It's texture is a bit different, more like tuna, and it can't be sliced.
The dill and mustard sauce I have not yet tried to make, as there is a very nice one they sell in Sainsbury's where they call it just Dill sauce. And do go for the Sainsbury's own, sometimes there is a different brand which costs more and doesn't taste like it should.
Finally boil some potatoes or make Hasselback potatoes:
Roasting potatoes, e. g. King Edward, enough for everyone. The potatoes should be medium or large sized.
- Peel the potatoes and wash.
- Take a skewer and pierce through a potato along it's flattest side, but about 1 cm into it.
- With a knife, cut thin (2-3 mm) strips so that the knife stops at the skewer. This will make the potato look a bit like a toast rack.
- Pre-heat the oven at 220 degrees C / gas mark 7.
- Place on a deep-ish baking tin with the cut side up and pour a little grapeseed oil on top of each potato. With a brush, spread the oil so that the potatoes are well covered.
- Place in the middle of the oven and bake until the potatoes are ready and have a nice golden brown colour. About 1 h and 15 minutes for medium sized potatoes.
- During baking, take out and brush with the oil two or three times, when they start to look a bit dry. The potatoes will start opening where they have been cut, so just dip the brush in the oil in the pan and dab the potatoes.