Prepare the Beef:

Season beef slices with salt and pepper.

Lightly dredge in flour if desired for extra browning.

Sear the Beef:

Heat oil or butter in a large skillet over medium-high heat.

Sear beef slices 2–3 minutes per side until browned. Remove and set aside.

Cook Onions & Garlic:

In the same pan, add onions and cook until soft and golden.

Add garlic and paprika; cook 1 minute until fragrant.

Make the Sauce:

Pour in beef broth and mustard (if using).

Stir, scraping up browned bits from the pan.

Simmer the Beef: