Pat the beef dry with paper towels and cut it into evenly sized 1-inch pieces.
Season the beef with smoked paprika, black pepper, and salt, then toss with approximately 1 teaspoon of the olive oil.
Heat a large skillet over medium-high to high heat until hot.
Add the beef in a single layer, working in batches if necessary. Sear for about 2 minutes before turning and browning the other sides.
Transfer the browned beef to a clean plate and set aside.
Add the remaining olive oil to the skillet if needed, then add the sliced mushrooms.
Cook the mushrooms without constantly stirring until their moisture evaporates and the edges become golden brown.
Add the sliced onion and cook for 3–4 minutes until softened.
Add the minced garlic, thyme, rosemary, and smoked paprika and cook for 30–60 seconds until fragrant.
Pour in the beef broth, Worcestershire sauce, and Dijon mustard, scraping the browned bits from the bottom of the skillet.
Return the seared beef and any accumulated juices to the skillet.
Simmer gently for 3–5 minutes, until the sauce reduces slightly and coats the beef and mushrooms.
Remove the skillet from the heat. If using Greek yogurt, mix a little warm sauce into the yogurt before stirring it back into the skillet.
Taste and adjust the seasoning. Add a small squeeze of lemon juice if desired.
Serve immediately with your preferred vegetable, cauliflower mash, rice, potatoes, or salad.