FOR PECAN BUTTER: Using on/off turns, finely chop pecans in processor. Add next 3 ingredients: process until blended. (DO AHEAD: Can be made 2 hours ahead. Let stand at room temperature.)

FOR SAUCE: Heat oil in large saucepan over medium heat. Whisk in flour. Stir constantly until golden, about 10 minutes. Gradually whisk in clam juice; bring to boil, stirring constantly. Reduce heat to low; simmer until liquid is reduced to 1 cup, about 30 minutes. Increase heat to medium. Whisk in butter a few pieces at a time. Whisk in 1 tablespoon Worcestershire sauce, parsley, and lemon juice. Season sauce with salt, pepper, and Worcestershire sauce, if desired.

FOR TROUT: Whisk milk and eggs in medium bowl to blend. Whisk flour, garlic powder, salt, pepper, and cayenne in large bowl. Working with 1 trout fillet at a time, dredge in flour mixture, shaking off excess. Dip fillet into milk mixture, then again into flour mixture.

Melt butter in large skillet over medium-high heat. Working in batches, add fillets to skillet and cook until golden and cooked through, about 3 minutes per side. Place 1 fillet on each of 6 plates. Spread about 1 tablespoon pecan butter over each fillet. Spoon some sauce over, sprinkle with toasted pecans, and garnish with lemon wedges and parsley. Serve, passing remaining sauce alongside.