Preheat oven to 350 degrees. Blend 2 Tbs. margarine with softened cream cheese. Add beef, salt, pepper, milk, and onion mixing well. Separate crescent dough into 4 rectangles; firmly pressing perforations to seal. Spoon 1/2 C. meat mixture onto center of each rectangle. Pull all 4 corners of dough to top center, twist slightly, and seal edges. Brush top with reserved 1 Tbs. margarine and dip in crouton crumbs. Bake on ungreased cookie sheet for 20 to 25 minutes until golden brown. Makes 4 sandwiches.