Cut sirloin steak into uniform bite-sized pieces and season with kosher salt, black pepper, smoked paprika, and garlic powder. Let sit for 5 minutes.

Heat a large skillet over medium-high heat and add olive oil and unsalted butter. Allow the butter to melt and bubble.

Add seasoned steak bites in batches to the skillet and sear for approximately 3 minutes on each side until golden-brown. Remove and keep warm.

In the same skillet, reduce heat to medium and add remaining unsalted butter and minced garlic. Sauté until fragrant, about 1 minute.

Pour in beef broth, scrape the skillet to incorporate browned bits, then stir in heavy cream and simmer for 2 minutes.

Remove from heat and whisk in grated Parmesan cheese until smooth. Adjust with more cream or broth if needed.

Return steak bites to the skillet, toss to coat in the sauce, and warm through for 1 minute. Garnish with parsley and red pepper flakes.