1. Peel one half of the lime, removing all the white pith; dice the perch fillets.
2. Marinate the perch fillets in the cream with a squeeze of lime; set aside.

Mache velouté

1. Reduce the white wine and fish stock by half with the shallot, mushroom and some coarsely cracked black pepper; add the mache and purée.
2. Emulsify with olive oil, season with fleur de sel and a squeeze of lime juice.

Cooking the fish

1. Preheat a non-stick skillet and roast the perch fillets in the clarified butter, flesh side down. Turn them and finish cooking with the cold butter. Remove the fillets and set aside.
2. Add the diced lime and parsley to the skillet; foam the cooking butter and pour over the perch fillets.

Finishing

1. Serve the perch fillets with a little butter and the lime garnish.
2. Serve with the mache sauce.