Preheat the oven to 180°C.
Coat potato slices with melted butter and season with salt and pepper.
Arrange potatoes on a tray to form two 12cm discs.
Bake discs for 35 minutes until tender, then cool and chill.
Mix crème fraîche, spring onion, capers, lemon juice, and dill.
Fold flaked hot-smoked salmon into the cream mixture.
Compress mixture into 9cm chefs' rings and chill for at least one hour.
Whisk egg yolk, vinegar, mustard, sugar, salt, and pepper for the dressing.
Slowly whisk oil into the yolk mixture until creamy.
Stir in chopped dill and season with sea salt.
Fry chilled potato galettes in a pan for 5 minutes per side until warmed.
Combine drained fennel, apple, parsley, and lemon juice for the salad.
Place salmon tian on the galette and serve with salad and dressing.