Pat the beef pieces thoroughly dry with paper towels and season them generously with salt and pepper.

Heat 1 tablespoon of olive oil in your skillet over medium-high heat until it shimmers. Working in batches so you don't crowd the pan, brown the beef on all sides for about 2 minutes per side, then set it aside on a plate.

Add the remaining 1 tablespoon of oil to the same skillet and reduce the heat to medium. Stir in the diced onion and cook for 3 minutes until it softens, then add the minced garlic and cook for another 30 seconds until fragrant.

Toss in the sliced mushrooms and cook for 4 to 5 minutes, stirring occasionally, until they release their moisture and begin to brown.

Pour in the beef broth and scrape the bottom of the skillet with your wooden spoon to release all the browned bits stuck to the pan.

Return the browned beef to the skillet along with the Worcestershire sauce, dried thyme, and paprika. Stir everything together and bring the mixture to a gentle simmer.

Stir in the uncooked rice, breaking up any clumps with your spoon, and ensure the rice is mostly submerged.

Cover the skillet with a lid, reduce the heat to low, and let everything simmer for 18 to 20 minutes without peeking.

While the mixture simmers, whisk the cornstarch and water together in a small bowl until smooth.

When the rice is tender and most of the liquid is absorbed, stir in the cornstarch slurry and cook uncovered for 2 to 3 minutes until the gravy thickens.

Stir in the frozen peas if using, and cook for 1 minute to heat them through. Taste and adjust salt and pepper, then transfer to serving bowls and garnish with fresh parsley.