Place chopped pecans in a shallow dish. Add egg whites to a separate dish and season with salt & pepper. Dip trout fillets in egg whites, then dredge flesh sides in chopped pecans. Reserve.
Serve on a bed of spinach leaves and thinly sliced red onion, drizzled with maple balsamic vinegar.
Notes
To make a balsamic reduction, heat good quality balsamic vinegar in a small saucepan over medium heat. Gently simmer until reduced by half and slightly thickened.