Remove the fish from the foil, cover and allow to defrost for approx. 2 hours. Wash the cucumber thoroughly, dab dry and cut in half lengthwise. Remove the seeds with a teaspoon. Cut the cucumber into pieces.
Dab fish dry and fry in 2 tablespoons of hot oil on both sides for about 6 minutes. Season with salt and pepper. Fry the cucumber briefly in the remaining oil in a saucepan, add cream cheese and 100 ml water and mix.
Season if necessary and braise for about 5 minutes. Mix the frozen herbs and mustard. Brush the fish with it shortly before the end of the cooking time. Arrange one piece of salmon fillet each with cucumber vegetables and lemon wedges.