Step 1:

Start by seasoning the sirloin steak slices generously with salt and pepper on both sides. Allow them to sit at room temperature for about 15-20 minutes to enhance their flavor and tenderness.

Step 2:

In a large skillet, heat the olive oil over medium-high heat. Once hot, add the seasoned steak slices and sear them for about 3-4 minutes on each side, depending on your desired level of doneness. For medium-rare, aim for an internal temperature of 135°F (57°C). Once cooked, remove the steak from the skillet and set aside, covering it loosely with foil to keep warm.

Step 3:

In the same skillet, add the butter and minced garlic. Sauté for about 1 minute, allowing the garlic to become fragrant but not browned. This will create a flavorful base for your sauce.

Step 4:

Add the sliced mushrooms to the skillet and cook for 4-5 minutes, stirring occasionally, until they are tender and browned. Then, pour in the beef broth, scraping the bottom of the skillet to deglaze and incorporate any flavorful bits stuck to the pan.

Step 5:

Lower the heat to medium and add the heavy cream, Worcestershire sauce, and red pepper flakes (if using). Stir the mixture, then bring it to a gentle simmer. Allow it to cook for another 3-5 minutes, stirring frequently, until the sauce thickens slightly. Finally, stir in the grated Parmesan cheese until melted and smooth.