Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Line a grease pan (deep baking tray) with baking paper. For the lemon potatoes, wash the potatoes and dab dry.
Mix with garlic cloves and 3 tbsp. oil. Season with sea salt. Spread on the fat pan. Bake in a hot oven for about 45 minutes until golden brown, turning in between.
For the spice crust, wash herbs, shake dry and chop coarsely. Wash lemons hot, dry. Cut 1 lemon into thin slices. Peel of 1 1⁄2 Finely grate lemons. Squeeze both lemons.
Coarsely crush peppercorns and fennel seeds in the mortar. Mix with lemon peel, lemon juice, up to 2 tablespoons, herbs, up to 1 tablespoon, and 3 tablespoons of oil.
Line a baking tray with baking paper for the fish. Rinse the fish, dab dry and season with salt. Place the fish on the baking tray with the meat side up. Spread the spice mix over it. After about 25 minutes baking time, spread lemon wedges between the potatoes and put the fish under the potatoes in the oven.
Bake for about 20 minutes. After 10 minutes change the trays so that the fish is on top. Mix the crème fraiche with the rest of the herbs and lemon juice. Season with salt, pepper and 1 pinch of sugar. Arrange everything.