Heat olive oil in a large skillet over medium-high heat. Add the beef slices and sear until browned, about 2–3 minutes per side. Remove and set aside.
In the same skillet, add butter, onions, and garlic. Sauté for 2 minutes until fragrant.
Add sliced mushrooms and cook until tender and browned, about 5 minutes.
Stir in paprika and thyme, then pour in the beef broth to deglaze the pan. Scrape up all the browned bits.
Reduce heat to medium-low, stir in heavy cream, Parmesan, and Dijon mustard. Simmer gently until sauce thickens (3–5 mins).
Add spinach and stir until wilted. Return beef to the pan, toss to coat with sauce.
Simmer another 2 minutes to warm through. Season with salt and pepper.
Garnish with fresh parsley before serving.
Prep Time: 10 mins
Cooking Time: 20 mins
Total Time: 30 mins
Kcal: 460
Servings: 4