Defrost peas at room temperature. For the salsa, wash the herbs, shake dry and remove leaves, except for some mint for garnishing, from the stalks and chop finely. Wash lemon hot, grate dry, grate peel thinly, cut fruit in half, squeeze juice from one half. Mix chopped herbs, lemon peel, 1-2 tbsp. lemon juice and 4 tbsp. olive oil. Season to taste with salt and pepper.
Mash the defrosted peas as finely as possible. Whip cream until stiff and fold into the pea mixture in 2 portions. Wash the mussels, dab dry and season with salt. Heat 2 tablespoons of oil and fry the mussels for about 2 minutes on each side. Arrange mousse, mussels and salsa and season with pepper.