Boil salted water; cook tortellini per package until al dente. Drain, drizzle with oil, set aside.
Pat steak dry. Heat oil in skillet over medium-high. Season steak; sear in batches 2–3 min per side. Remove to plate, cover with foil.
Lower heat to medium. Melt butter, add garlic, cook 30–60 sec until fragrant.
Stir in cream (add broth if too thick). Simmer 2–3 min to thicken.
Gradually add Parmesan; stir until smooth. Season to taste.
Add tortellini and steak; toss gently 1–2 min to coat and warm.
Garnish with parsley and serve hot.