Pulse nuts in a food processor with 1/4 cup of flour until finely ground. Rinse trout and pat dry. Season with salt inside and out.
Put the remaining 2 cups flour in a pie plate. Beat the egg in a pie plate. Spread ground nuts on a dinner plate. Dip both sides of trout first in flour (pat off the excess), then egg, and then nuts. Heat oil in a 12-inch heavy skillet over moderate heat until hot but not smoking and cook trout, shaking skillet to prevent sticking and turning once with a metal spatula, until browned on both sides and just cooked through, about 12 minutes total.
While trout is cooking, melt butter in a small saucepan and stir in lemon juice. Season with salt and pepper and keep warm. Pour over trout and sprinkle fish with parsley.
Recipe courtesy Gourmet Magazine
Recipe courtesy of Emeril Lagasse