Season chicken with salt and pepper. Melt butter in a large pot over medium-high heat. Cook chicken 6–8 minutes until browned; remove and set aside.
Add a bit more butter to the pot. Sauté minced garlic for 30 seconds until fragrant. Stir in crushed red pepper flakes.
Pour in chicken broth, scraping browned bits. Stir in heavy cream and bring to a gentle simmer.
Add tortellini and cook 4–6 minutes until tender.
Return chicken to the pot. Stir in Parmesan until melted. Heat 2–3 minutes and top with fresh herbs.