Bring a large pot of salted water to a boil. Add the tortellini and cook according to package instructions, usually about 3-5 minutes until they float to the top. Drain and set aside, reserving about ½ cup of pasta water.

While the pasta cooks, season your sliced steak generously with salt and pepper. In a large skillet, heat 1 tablespoon of olive oil over medium-high heat. Add the steak in a single layer and sear for 2-3 minutes per side, or until browned but still tender. Remove steak from pan and set aside.

Reduce heat to medium and add the butter along with the remaining tablespoon of olive oil to the same skillet. Once melted, add the minced garlic and sauté for about 1 minute until fragrant but not browned.

Pour in the heavy cream and stir well, scraping up any browned bits from the pan. Let the sauce simmer gently for 3-4 minutes, allowing it to thicken slightly.

Stir in the Parmesan cheese and crushed red pepper flakes, if using. Adjust seasoning with salt and pepper to taste. If the sauce feels too thick, add reserved pasta water a little at a time until you reach your desired consistency.

Add the cooked tortellini and seared steak back into the skillet. Toss gently to coat everything evenly in the creamy garlic sauce. Warm through for 1-2 minutes.

Remove from heat, sprinkle with fresh parsley, and serve immediately.