Brown the beef (optional): Heat a skillet over medium-high heat. Sear shaved beef or ground beef until lightly browned. Drain excess fat.
Layer ingredients in Crock Pot: Add the beef, sliced onions, peppers, mushrooms, beef broth, garlic powder, Italian seasoning, salt, and pepper to the slow cooker. Stir to combine.
Cook: Cover and cook on low for 6–7 hours or high for 3–4 hours until the beef and vegetables are tender.
Make the sauce creamy: Stir in cream cheese until melted and smooth. Add shredded mozzarella (or provolone) and mix well.
Add tortellini: Stir in the tortellini during the last 20–30 minutes of cooking. Cook until pasta is tender but not mushy.
Finish and serve: Top with extra cheese if desired. Garnish with fresh parsley before serving.