I suppose you're gonna use large pieces of salmon or a whole salmon. I read you use frozen fish; you will need to defrost it first.
Mostly some sort of "court bouillon" is used to poach the fish in, nothing more than flavored water. I learned from Gordon Ramsey's earliest cookbook to make a very flavorful but not so traditional court bouillon; plenty water enough to submerge the salmon entirely, lemon zeste, lemon juice, whole black pepper corns crushed, I use also a few sezuan peppercorns, some fennel seeds, some koriander seeds, one star anice (absolutely no more!), a few green kardemom pods just cracked a little, a few whole all spice corns, a halved onion, salt. Let it all simmer for a while and... taste it! May sound a little weird, but you really need to taste to check for the salt content and all other flavoring. If your court bouillon don't taste right, the fish won't either.
Bring this court bouilon to a boil and add the salmon. Take away from the heat, cover and let it sit until completely cooled. You now should have perfectly poached salmon. Keep the salmon in the liquid until needed, to prevent from drying out!!
For your cold sauces;
- dill sauce; 50/50 crème fraîche (or yoghurt) + mayo, s&p, (optional) smallest tsp of ouzo or similar, finely chopped dill, lemon juice.
- mustard sauce; mayo, dash of tarragon vinegar, Dijon mustard to taste, grainy mustard to add some other texture. Add very little water at room temperature to dilute if needed.
- cocktail sauce; mayo, ketchup, tbsp of cognac or brandy or bourbon or whisky , tbsp of madeira wine or port wine or medium sherry..., pinch of cayenne, s&p.