In a large skillet melt remaining 1 Tbsp Butter and sauté onion over medium heat until tender.
Add Crab. Mushrooms, Cracker Crumbs, Parsley, Salt, Pepper and 2 Tbsp of the prepared white sauce. Heat through.
Preheat oven to 350 degrees F
Pound Chicken Breasts to 1/4 inch thickness.
Spoon about 1/4 of the Crab mixture onto the edge of each Chicken Breast.
Roll up and secure with toothpicks.
Place Chicken Rolls in a lightly greased 9x13 inch baking dish, then top with the remaining white sauce.
Cover dish and bake at 350 degrees F for 30 minutes or until Chicken juices run clear.
Sprinkle with Cheese and Paprika and bake, uncovered, for another 5 minutes or until Cheese is melted and bubbly.
Remove toothpicks and serve.