Shrimp Artichoke Casserole

1 (14 ounce) can artichoke hearts, drained and quartered
1/2 cup (1 stick) margarine, divided
1 pound headless shrimp, peeled
8 ounces fresh mushrooms, sliced, or
    1 (8 ounce) can mushroom pieces
1/4 cup flour
1 cup half-and-half
1/2 cup milk
3 ounces Monterey jack cheese, cubed
1 teaspoon salt
1/2 teaspoon pepper
1/4 cup dry sherry
1/2 teaspoon Worcestershire sauce
Paprika

Place artichoke hearts in bottom of a 1 1/2-quart casserole.

In a skillet, melt 1/4 cup margarine and saut