To make the grilling sauce, combine the olive oil, lime juice, red onion, tarragon, salt, and white pepper in a medium-size bowl and mix thoroughly with a whisk.
Brush the trout fillets with the sauce and place (top side down) on a hot, oiled grill. Turn after about five minutes, or when the fish is halfway cooked. After turning, brush the tops of the fillets with a small amount of additional grilling sauce. Continue cooking for about five more minutes, or until the fish is fully cooked through. Garnish with a sprinkling of fresh chopped tarragon and a slice of lime.
Makes: 6