Season the diced top sirloin steak generously with kosher salt and freshly ground black pepper. In a large Dutch oven, heat olive oil over medium-high heat. Once the oil shimmers, add the steak and sear for about 6–8 minutes until browned on all sides. Remove the meat and set aside.

Reduce the heat to medium and add chopped medium sweet onion, diced large carrots, and diced celery to the pot. Sauté for 3–4 minutes until they start to soften and the onion becomes translucent.

Stir in minced garlic and sliced cremini mushrooms. Cook for another 3–4 minutes, allowing the mushrooms to brown and release their moisture.

Whisk in all-purpose flour and tomato paste, ensuring everything is well-coated. Cook for about 1 minute, stirring constantly.

Pour in dry red wine to deglaze the pot, scraping the bottom with a wooden spoon. Add beef stock, fresh thyme, and bay leaves, along with the seared steak. Bring to a boil, then reduce heat to low and let simmer for 30 minutes.

After 30 minutes, add large russet potato chunks. Stir well and simmer for another 20 minutes until the potatoes are fork-tender. Remove the bay leaves and thyme sprigs.

Taste the stew and adjust seasoning, adding more salt or pepper if necessary. Sprinkle chopped fresh parsley over the stew before serving.