Arrange a rack in the middle of the oven and heat the oven to 350ºF.

Prepare the following, adding each to the same large bowl as it is completed: Dice 6 ounces small or baby Yukon Gold potatoes. Peel and dice 2 medium carrots (about ¾ cup). Dice 2 medium celery stalks (about 1 cup), and 1 medium yellow onion (1 ¼ to 1 ½ cups).

Finely grate or chop 2 garlic cloves. Trim off any surface fat from 1 pound beef chuck, then cut into ¾-inch cubes. Pat dry with paper towels and season with 1 teaspoon of the kosher salt and ½ teaspoon of the black pepper.

Heat 1 tablespoon of the olive oil in a Dutch oven over medium-high heat until shimmering. Add half of the beef in an even layer and sear until browned on two sides, 2 to 3 minutes per side. Using a slotted spoon, transfer to a plate. Add ½ tablespoon of the olive oil to the pot and repeat browning the remaining beef, reducing the heat as needed if the pot starts to smoke. Transfer to the plate.

Reduce the heat to medium. Add the remaining 1 ½ tablespoons olive oil, remaining ¼ teaspoon kosher salt, 3 large fresh thyme sprigs if using, 2 dried bay leaves, and carrot mixture to the pot. Cook, stirring occasionally and scraping up the browned bits from the bottom of the pot with a wooden spoon, until the vegetables start to soften at the edges, about 5 minutes. Add the garlic and cook until fragrant, about 1 minute.

Return the beef and any accumulated juices to the pot. While stirring continuously, add 2 tablespoons tomato paste and sprinkle with 3 tablespoons all-purpose flour. Cook until flour is combined and the tomato paste slightly darkens in color, about 2 minutes.

Increase the heat to medium-high. Add 1 cup Guinness and cook, stirring continuously, until the liquid thickens and reduces so significantly it almost disappears, about 2 minutes. Add 2 cups beef broth and 2 tablespoons Worcestershire sauce, stir to combine, and bring to a simmer.

Cover and transfer the Dutch oven to the oven. Bake until the beef is tender, about 1 ½ hours.

Remove the Dutch oven from the oven. Increase the oven temperature to 400ºF. Place 1 large egg with 1 teaspoon water in a small bowl and whisk with a fork until the egg is beaten up.

Remove and discard the thyme sprigs and bay leaves from the filling. Add 1 cup frozen peas and stir to combine. Taste the filling and season with more kosher salt as needed.

Fit a strainer or colander over a large bowl. Pour the filling into the strainer (you should have about 1 ¾ cups gravy). Transfer the beef mixture to a 10-inch cast iron skillet or 9 ½-inch deep dish pie dish. Pour over ¾ cup of the reserved gravy into the skillet and stir to combine. Spread the filling into an even layer (save the remaining gravy to serve alongside the pie).

Unfold 1 pie crust. If it is less than 10-inches in diameter, dust the counter with all-purpose flour and roll it out until 10-inches wide. Place the crust over the filling. Press the crust gently down onto the surface of the filling, then press against the edge of the skillet all the way around to seal. Brush the crust with the egg wash. Use a sharp knife to cut 5 (1-inch) slits in the top of the crust to vent.

Place the skillet on a rimmed baking sheet. Bake until the crust is a deep golden brown, about 30 minutes.

Remove the pie from the oven. Sprinkle with fresh thyme leaves if desired. Let rest for 5 to 10 minutes before serving. Meanwhile, rewarm the reserved gravy in the microwave for 1 to 2 minutes or in a small saucepan over medium heat for 2 to 3 minutes. Serve the pot pie with a small drizzle of gravy on top to be passed at the table.