In a large bowl, combine the cubed beef with flour, salt, black pepper, garlic powder, and onion powder. Toss until the beef is evenly coated.

Heat the olive oil in a large skillet or Dutch oven over medium-high heat. Add the coated beef and sear until browned on all sides. Once browned, remove the beef from the skillet and set it aside.

In the same skillet, add the diced onion, sliced carrots, and celery. Sauté until the vegetables are softened, about 5 minutes. Add the minced garlic and cook for an additional minute until fragrant.

Pour in the beef broth, grape juice, and tomato paste. Stir well to combine, scraping any browned bits from the bottom of the skillet. Add the dried thyme and rosemary, and bring the mixture to a simmer. Return the seared beef to the skillet and stir to combine. Let the mixture simmer for 10-15 minutes, or until the gravy has thickened.

Stir in the frozen peas and corn, and cook for an additional 5 minutes.

Preheat your oven to 375°F (190°C). Transfer the beef and vegetable mixture to a large baking dish or individual ramekins. Roll out the puff pastry sheet and place it over the top of the filling, trimming any excess dough. Brush the pastry with the beaten egg to give it a golden finish.

Bake in the preheated oven for 25-30 minutes, or until the pastry is golden brown and flaky. Allow the pot pie to cool for a few minutes before serving.