Place tofu and garlic in a food processor, and process until smooth. Add sour cream, mustard, and lemon juice; process until blended. Stir in chives, dill, and 1/2 teaspoon ground peppercorns. Cover and chill.
Preheat oven to 450°.
Place the salmon, skin side down, on a baking sheet coated with cooking spray. Brush fillet with oil; sprinkle with 1 1/2 teaspoons ground peppercorns and salt. Bake at 450° for 12 minutes or until fish flakes easily when tested with a fork. Serve sauce with salmon. Garnish with rosemary sprigs, if desired.