01 - Bring a large pot of salted water to a boil. Cook the cheese tortellini according to package instructions until tender. Drain thoroughly and set aside.
02 - Pat the sirloin pieces dry and season generously with salt and freshly ground black pepper. Heat olive oil in a large skillet over medium-high heat until shimmering. Add the steak pieces in a single layer and sear for 2–3 minutes per side until a deep golden-brown crust forms and the meat reaches your preferred doneness. Transfer the steak to a plate and tent loosely with foil.
03 - Reduce the skillet heat to medium. Add the unsalted butter and let it melt until foaming. Add the minced shallots and garlic, stirring frequently, and cook for about 1 minute until fragrant and softened, being careful not to let the garlic brown.
04 - Pour the heavy cream into the skillet, scraping up any browned bits from the bottom of the pan. Stir to combine and bring the mixture to a gentle simmer. Cook for 2–3 minutes, allowing the sauce to reduce and thicken slightly.
05 - Gradually stir in the grated Parmesan cheese, continuing to stir until it is fully melted and the sauce is smooth and velvety.
06 - Return the cooked tortellini and seared steak pieces to the skillet. Toss gently to coat everything evenly in the garlic cream sauce. Cook for 1–2 minutes over low heat just until everything is warmed through.
07 - Transfer to warm serving plates or a large serving bowl. Sprinkle generously with chopped fresh parsley and serve immediately.