Grilled Salmon Fillets with Creamy Horseradish Sauce

Sauce:
    3/4 cup sour cream
    1/4 cup mayonnaise
    2 tablespoons prepared white horseradish
    2 tablespoons chopped fresh basil
    1 tablespoon fresh lemon juice
    1 teaspoon soy sauce

Salmon:
    Nonstick vegetable oil spray
    3 tablespoons vegetable oil
    1 tablespoon prepared white horseradish
    1 tablespoon soy sauce
    1 small garlic clove, minced
    1/2 teaspoon salt
    1/4 teaspoon coarsely ground black pepper
    6 (1-inch-thick) salmon fillets (each about 6 ounces)

For sauce: Mix all ingredients in small bowl. Season with salt and
pepper. (Can be made 1 day ahead. Cover and chill.)

For salmon: Spray grill rack generously with nonstick spray. Prepare
barbecue (medium-high heat). Whisk oil, horseradish, soy sauce,
garlic, salt, and pepper in another small bowl. Brush oil mixture
over both sides of salmon fillets. Grill salmon just until opaque in
center, about 4 minutes per side. Transfer salmon to plates. Serve
with sauce.