Sauté onion in hot oil in a large skillet over medium-high heat 5 minutes or until golden brown. Stir in flour, and cook, stirring constantly, 1 minute. Gradually stir in barbecue sauce and beef broth; cook, stirring constantly, 3 minutes or until mixture begins to thicken.
Stir in pork, and bring to a boil. Remove from heat, and spoon mixture into a ligihtly greased 13- x 9-inch baking dish.
Spoon Mashed Potato Crust evenly over hot barbecue mixture.
Bake at 425º for 15 minutes.