Stuffed Pork with butter

1/4 cup butter 1 onion , finely chopped 3 garlic cloves , minced 1 (10 ounce) package frozen chopped spinach , thawed and squeezed dry 1 (12 ounce) package[...]

2 pork tenderloin (3/4 lb. each) 2 tablespoons butter or 2 tablespoons margarine 1/4 cup celery , finely chopped 2 tablespoons onions , finely chopped 1[...]