Thaw shrimp, if frozen. Peel and devein shrimp. Rinse shrimp; pat dry with paper towels. Set shrimp aside. In a very large skillet heat oil over medium heat. Add chorizo, onion, and garlic to skillet. Cook for 5 minutes, stirring occasionally. Add tomatoes, broth, and saffron to skillet. Bring to boiling; stir in the couscous. Reduce heat. Simmer, covered, for 5 minutes.
Add shrimp, chicken, and peas to skillet; cover and cook about 5 minutes more or until shrimp are opaque and couscous is tender. If desired, garnish with parsley.