Boil the lentils for 15 minutes until just tender. Drain, then toss with the lemon juice, garlic and some seasoning while still warm.
Meanwhile, heat the grill to high. Put the salmon on a non-stick baking sheet and sprinkle with the garam masala. Grill for 5 minutes until the top is golden and the salmon is cooked through.
Mix ½ the mint with the yoghurt and season. Toss the lentils with the rest of the mint and the parsley. Flake the salmon and toss with the lentils. Serve with the mint yoghurt and lemon wedges.