Maryland Crab with butter

1/3 cup mayonnaise 1 1/2 teaspoons seafood seasoning (like Old Bay) 1 tablespoon capers , drained 1/2 teaspoon Worcestershire sauce 1 teaspoon Dijon mustard 1[...]

2 tablespoons finely chopped onions 3 tablespoons butter 2 cups crabmeat (2 6-oz cans) 1/2 teaspoon salt 1/4-1/2 teaspoon ground black pepper 3 cups milk 1/2[...]