Sprinkle one side of the salmon with 2 tsp Dill, salt and pepper. Grill the salmon for 15-20 minutes, turning occasionally until cooked.
Add the mustard, remaining ½ tsp Dill and cream to a pan, season with salt and pepper. Bring to the boil. Stir in the yoghurt and gently heat through without boiling. Serve with the salmon.