Adopted from https://cooking.nytimes.com/recipes/1012397-guinness-pie but updated some instructions and documenting to get around the paywall.

Total time: 4 hours cooking, dough will need to rest 2 hours in the fridge.
Ingredients:
For the stew:
- 2 large red onions, chopped
- 4 tablespoons butter
- 4 cloves garlic, minced
- 2 carrots, peeled and chopped
- 2 ribs celery, chopped
- 10 mushrooms, trimmed and sliced
- 3 pounds brisket (preferably second-cut) or stew meat, chopped into bite-size pieces
- Kosher salt
- Freshly ground black pepper
- 2 tablespoons flour
- 1 sprig rosemary
- About 4 cups (2-3 cans) Guinness or other stout
- 8 ounces freshly grated Cheddar
- 2 tbsp tomato paste
- Oven safe pot with a lid, like a dutch oven
For the Pastry:
The original recipe calls for no bottom crust; should you want a bottom crust double this list:
- 187 g all purpose flour
- 10 g baking powder
- 5 g salt
- 1/2 cup (1 stick) very cold unsalted butter
- 1 egg yolk, lightly beaten
- 9 inch deep dish pie pan
Cooking Instructions:
For the Stew
- Preheat the oven to 375 degrees.
- In a large, overproof pot fitted with a lid, get a browned sear on the meat; remove and set aside. This meat will be stewing so no need to do more than get some color on it for flavor.
- In the same pot heat 2 tablespoons of the butter over medium-low heat. Add the onions and cook, stirring frequently, until soft, about 10 minutes.
- Add the carrots, celery, mushrooms and remaining 2 tablespoons butter and cook over medium heat, stirring frequently, until the mushrooms are dark in color and the moisture released by them has evaporated, about 15 minutes.
- Add in the garlic and stir frequently, about 2 minutes. Don’t let it burn or it may turn out slightly bitter.
- Add the beef, flour and rosemary to the pan and cook over high heat, stirring often, for about 5 minutes.
- Add enough Guinness to just cover the beef. Cover the pan and put it in the oven for 1½ hours.
- If you have not yet started the pastry! Now is the time!
- Remove from the oven and stir. Taste and add salt and pepper to taste. If bitter at this stage, add 1-2 tbsp of tomato paste to taste. Return to the oven and cook for 1 hour more.
- Add the cheddar and stir. Season to taste with salt and pepper.
For the pastry:
This pastry can be made ahead of time, it needs to rest for 2 hours in the fridge minimum.
- Sift together the flour, baking powder and salt into a bowl. Using a pastry cutter or your hands, quickly work the butter into the dough until it is the texture of coarse meal. Add ice water, a splash at a time, until a firm dough forms, try not to add so much it gets sticky. Wrap the dough in plastic and refrigerate for at least 2 hours.
- Place the dough between two sheets of plastic wrap or parchment paper and, using a rolling pin, roll to the thickness of a computer mouse pad. If making a bottom crust make two circles; one big enough for your inside pan and one for the top.
- If making a bottom crust: Add the bottom dough to your pan and parbake it: Add parchment paper over your crust and then add either pie weights or rice up to 3/4 the way up the pie sides. Bake for 15 minutes. Remove the pie weights or rice and bake for an additional 7 minutes.
- Pour the stew into your pie pan.
- Place the dough on top of the pie and pinch it closed around the edges using the tines of a fork, then slash the center lightly with a knife. Brush with the egg yolk, place on a baking sheet and bake for 40-45 minutes, or until the pastry is puffy and golden.