In a saucepan, over medium heat, combine the butter and flour. Stir until incorporated. Cook for 12 to 15 minutes for a dark roux. Stir in the stock. Season with salt and pepper. Bring the liquid to a boil. Reduce the heat to medium low and continue cooking for 15 to 20 minutes. Remove from the heat and keep warm. Peel the potatoes and cut fries, 4 inches by 1/2-inch. Bring a pot of salted water to a boil. Add the potatoes and blanch for 4 minutes. Remove, drain and cool completely. Fry the potatoes until golden brown. Remove and drain on paper towels. Season with salt and pepper. To serve, mound the fries into the individual (16-ounce) disposable cups. Spoon the gravy over the fries and crumble the cheese. Serve immediately.