Preheat the oven to 350 degrees.
In a large bowl mix the flour and garlic powder. Set aside.
Cut the roast into 1.5" - 2" cubes.
Place the beef into the flour mixture and toss to coat evenly.
Place a dutch oven (or large pan) over high heat. Once heated, add 1 tablespoon of butter and let melt to coat the bottom of the pan.
Add the beef to the hot pan and sear on each site until crispy (about two minutes per side).
Place the seared beef on a dinner plate and set aside.
Reduce the temperature to medium and add 1 tablespoon of butter followed by the onion and carrots. Cook for about 5 minutes until the carrots and onions are soft.
Add the garlic and cook an additional minute.
Add 1/2 cup of beer to deglaze the pan. Make sure to scrape the bottom with a wooden spoon.
If necessary, add another 1/2 cup (if the original amt. cooks off quickly).
Let cook for 2 minutes.
Stir in the Worcestershire Sauce, balsamic vinegar, tomato sauce, sugar, rosemary, bay leaf and thyme.
Add in the last cup of beer, beef broth, salt and black pepper and stir.
Add in the mushrooms and seared beef and stir.
Place the dutch oven in the oven and bake for 90 minutes (covered).
When done baking, mix the cornstarch with a tablespoon of water and add to the beef mixture. Set aside for 5 minutes to thicken.
Transfer the beef mixture to a pie dish or other deep dish container.
Turn the oven temperature up to 400 degrees.
Unfold the puff pastry and lay flat.
Beat the egg with a tablespoon of water and brush lightly across the puff pastry.
Place the puff pastry on top of the pie dish and, using a knife, poke a hole or two in the top (to allow air to escape).
Transfer the pie to the oven and bake for another 20-25 minutes until golden brown.
Remove from the oven and let sit 5 minutes before serving.
Add salt and pepper to taste.