1. Cook fries according to package directions, until crispy. Season with salt immediately after cooking. Meanwhile, prepare toppings.
2. Bring 1 1/2 cups of milk to a simmer in medium saucepan over medium-high heat. Whisk remaining milk with flour until smooth. When milk in pan is simmering, whisk in flour mixture until smooth. Reduce heat to medium and continue to cook, whisking constantly, until thickened, about 3 to 5 minutes. Remove from heat and whisk in cheeses. Season with salt, to taste, and keep warm.
3. Heat 1 tablespoon of oil in large skillet over medium-high heat. Add onion and cook until tender, 5 to 7 minutes. Add garlic and season with salt. Cook for an additional 2 to 3 minutes, until onions are very soft. Stir in Worcestershire sauce and remove onions from skillet.
4. Cut roast beef into 1” strips and add to same skillet with remaining oil over medium heat. Cook beef until just crisped, about 1 minute. Remove from skillet. Pour beef broth into same skillet, increase heat to high and bring to boil. Continue to boil until reduced by half. Stir in soy sauce and remove from heat.
5. Arrange fries on serving plate and top with cheese sauce, beef, onions and au jus. Garnish with fresh parsley and black pepper.