- 1/2 cup (1 stick) butter, room temperature
- 12 Kalamata olives or other brine-cured black olives, pitted, chopped
- 1 medium shallot, chopped
- 1 tablespoon chopped fresh Italian parsley
- 2 teaspoons Dijon mustard
- 8 6- to 8-ounce salmon fillets (each about 1 1/4 to 1 1/2 inches thick)
- 2 1/2 cups orzo (rice-shaped pasta; about 1 1/4 pounds)
- Whole Kalamata olives (optional)
- Fresh Italian parsley sprigs (optional)
Mix first 5 ingredients in processor until well blended but still slightly chunky, occasionally scraping down sides of bowl. Season butter mixture to taste with salt and pepper. Transfer to small bowl. DO AHEAD Olive-mustard butter can be prepared 2 days ahead. Cover and refrigerate. Soften slightly at room temperature before using.
Preheat oven to 400°F. Brush large rimmed baking sheet with olive oil. Arrange salmon fillets on prepared sheet; sprinkle with salt and pepper. Roast salmon just until opaque in center, about 14 minutes.
Meanwhile, cook orzo in large pot of boiling salted water until tender but still firm to bite. Drain; return orzo to same pot. Add half of olive-mustard butter and toss to coat.
Divide orzo among 8 plates. Top each serving with 1 salmon fillet. Place small dollop of olive-mustard butter atop each salmon fillet. Garnish with whole olives and parsley sprigs, if desired, and serve.