Sauce: In a medium bowl blend sour cream green onions and OLD BAY. Cover. Refrigerate until ready to serve.
Shrimp cakes: Mix flour OLD BAY and baking powder in large bowl. Stir in shrimp cooked rice and green onions. Add butter milk and eggs. Gently stir until blended.
Heat large nonstick skillet coated with no stick cooking spray on medium heat. Drop heaping tablespoonfuls of shrimp mixture into skillet. Flatten slightly so cakes are about 2 inches in diameter. Cook cakes in batches 5 minutes per side or until lightly browned.
Serve shrimp cakes with sauce.
Note: Recipe can be made up to 24 hours in advance. Cool wrap and store cakes in the refrigerator. Reheat on baking sheet in preheated 350° F oven for 10 minutes. Refrigerate sauce in a covered container.