Heat a large skillet or Dutch oven over high heat until just smoking. Add 1 tablespoon of the oil, then lay in the shaved beef in a single layer. Work in two batches if needed.
Season generously with salt and pepper and let it sear undisturbed for about 60 seconds, then quickly toss for another 30–45 seconds, just until browned. Transfer to a plate and set aside.
Reduce heat to medium-high. Add the remaining oil and the butter to the same pan. Once the butter melts, add the bell pepper and onion. Cook, stirring occasionally, until softened, about 6–7 minutes.
Stir in the garlic and cook for 30 seconds more. Season with a pinch of salt and pepper.
Pour in the Worcestershire sauce and beef broth, scraping up any browned bits from the bottom of the pan. Bring to a steady simmer.
Add the tortellini to the broth and stir to submerge. Cook, stirring occasionally, until the tortellini is tender and the broth has reduced and thickened slightly, about 5–7 minutes.
Pour in the heavy cream and stir gently. Let it come back to a gentle bubble and simmer for 1–2 minutes, until the sauce looks silky and clings to the tortellini.
Add the seared beef back to the pan along with any juices on the plate. Stir gently just until the beef is warmed through, about 1 minute. Taste and adjust salt and pepper.
Turn off the heat and lay the provolone slices in an overlapping layer across the top. Cover with a lid (or a sheet of foil) and let sit for 2–3 minutes, until the cheese is fully melted and gooey. Sprinkle with parsley if using.