Heat a large skillet over high heat; add butter, beef cubes, sweet potato, carrots, red potatoes, and yellow onion to the hot skillet. Sprinkle meat and vegetables with 1/2 teaspoon garlic powder and black pepper. Cook and stir until meat is browned on all sides, about 10 minutes. Transfer meat and vegetables to a 1-quart baking dish.
Whisk beer, brown gravy mix, 1/2 teaspoon garlic powder, thyme, and black pepper together in a saucepan over medium heat. Bring to a simmer, reduce heat to low, and cook, whisking constantly, until sauce has thickened, about 5 minutes. Pour sauce over meat and vegetables.
Trim puff pastry to fit top of baking dish and cover dish with pastry.
Bake in the preheated oven until puff pastry is deep golden brown and filling is bubbly, 45 to 50 minutes.