Cut the aromatics and beef. Dice 1 medium yellow onion, mince 2 garlic cloves, and place both in a medium bowl. Trim 3 pounds beef chuck of any surface fat, then cut it into 4 steaks.

Dry and season the beef. Pat the steaks dry with paper towels, then season all over with 1 ½ teaspoons kosher salt and ½ teaspoon black pepper.

Sear the beef in batches. Heat 1 tablespoon vegetable oil in an Instant Pot or electric pressure cooker on the Sauté setting until shimmering. Working in 2 or 3 batches, add the steaks in a single layer and sear undisturbed until browned on both sides, 4 to 5 minutes per side. Transfer with tongs to a plate. Repeat searing the remaining steaks, then transfer to the plate.

Soften the aromatics. Add the onion and garlic to the pot, and cook, stirring occasionally, until softened, about 4 minutes. Meanwhile, cut the vegetables.

Cut the vegetables. Peel 1 pound carrots and cut in half crosswise. Halve 1 pound red or Yukon Gold potatoes.

Add the seasonings and spices. Add 1 tablespoon tomato paste, 1 tablespoon Dijon mustard, ½ teaspoon dried oregano, and ½ teaspoon dried thyme to the onions and cook until the tomato paste is darkened in color, about 1 minute.

Deglaze the pot. Add ½ cup dry red wine and stir to combine, scraping up any browned bits. Simmer until almost evaporated, 2 to 3 minutes. Turn off the pressure cooker.

Add the broth and seared beef. Pour in ½ cup beef broth and stir to combine. Nestle the steaks evenly in the liquid and pour in any accumulated juices from the plate.

Top with the carrots and potatoes. Place the carrots and potatoes on top of the beef in an even layer but do not stir.

Cook on HIGH pressure for 35 minutes. Lock the lid on and make sure the pressure valve is set to seal. Set to cook for 35 minutes on HIGH pressure. It will take about 19 minutes to come up to pressure.

Naturally release pressure for 10 minutes and make the cornstarch slurry. When the cook time is up, let the pressure naturally release for 10 minutes. Meanwhile, stir 1 tablespoon plus 1 ½ teaspoons cornstarch and 2 tablespoons water together in a small bowl until the cornstarch is dissolved. Coarsely chop some fresh parsley leaves for garnish if desired.

Release the remaining pressure. Quick release any remaining pressure. Using tongs, transfer the vegetables to a serving platter. Transfer the beef to a clean cutting board.

Thicken the sauce. Turn on the Sauté function. When the sauce is simmering, stir in the cornstarch mixture and simmer until the sauce is thickened, about 2 minutes. Taste and season with salt and pepper as needed.

Shred the beef and serve. Shred the beef with two forks into large chunks. Place on top of the vegetables. Spoon some of the sauce over the pot roast and vegetables, and serve the rest on the side. Serve garnished with the parsley if desired.