If blue crabs aren't available in your area, substitute Dungeness or other fresh crabmeat.
Melt butter in a large skillet over medium-high heat; add green onions and garlic, and sauté until tender. Stir in flour, and cook 1 minute. Gradually stir in half-and-half and next 3 ingredients.
Gently fold in crabmeat without breaking up lumps. Pour into a lightly greased 8- x 8-inch baking dish. Bake at 350° for 40 minutes or until lightly browned and bubbly. Serve with crackers or toast points.