To prepare sauce, combine first 7 ingredients, stirring with a whisk. Remove 2 tablespoons sauce; set aside. Reserve remaining sauce for dipping.
Preheat oven to 425°.
To prepare shrimp, peel and devein shrimp, leaving tails intact.
Cook chopped onion in boiling water for 2 minutes or until tender. Drain and rinse with cold water; drain. Place onion in a large bowl.
Place chicken in a food processor; process until coarsely chopped. Add chicken, paprika, and next 11 ingredients (paprika through 2 garlic cloves) to onion; stir well.
Place the shrimp in a single layer on a large baking sheet coated with cooking spray. Arrange shrimp on their sides, so that each forms a "C" shape. Spoon a heaping tablespoon of chicken mixture into the center of each shrimp. Gently press the chicken mixture until it touches sides of shrimp.
Brush shrimp with 2 tablespoons sauce. Bake at 425° for 10 minutes or until shrimp are done and stuffing is firm. Serve with remaining 1/2 cup sauce. Garnish with cilantro sprigs, if desired.