1 Rinse fish fillets, pat dry and pull out any remaining pin bones with tweezers.
2 Season the flesh side of the fillets with salt and pepper and coat with the mustard.
3 Place the fillets with the smeared sides together.
4 Rinse and dry lemon and cut into slices. Place half of the slices in an oiled fish grill basket.
5 Place the double fillet in the fish grill basket and cover with the remaining lemon slices. Secure the grill basket closed and keep the fillets cold.
6 Rinse mint and parsley. Shake dry, pluck leaves and coarsely chop. Peel the garlic and finely chop.
7 Toast pine nuts in a dry frying pan. Pour onto a plate and allow to cool completely. Finely chop pine nuts.
8 Mix herbs, garlic and pine nuts in a bowl with the oil. Season with salt and pepper and set aside.
9 Grill trout on medium hot grill for 6-7 minutes on each side.
10 The fish is done when the skin can be easily removed. Serve with the pesto.