Preheat your oven to 220°c/200°c fan-forced. In a bowl, combine parsley, chives, dill, onion, chilli, garlic, mustard, lemon juice and half of the olive oil.
On a board, place 1 of the salmon fillets, skin side down. Then, top with 2/3 of the herb mixture. Place the remaining salmon fillet, skin side up, on top of the herb mixture. Tie fillets together with kitchen string at 3 cm intervals. Rub with the remaining olive oil. Then, place on a baking dish.
Cook for 15 minutes. Remove from the oven and cut into 8 slices. Serve with lemon wedges and remaining parsley mixture.