Place the frozen, boneless, skinless chicken breast in the crockpot. Add 2 1/2 cups of warm Alfredo sauce.
Cover and cook on high for 6-8 hours, until fully cooked. Separate frozen chicken breasts that are stuck together after a couple of hours of cooking, if necessary. (If using thawed chicken breasts, cook on low for 4-6 hours)
Tear or cut the chicken into pieces.
Add 1 cup Alfredo sauce, minced garlic, black pepper and refrigerated three cheese tortellini. Cover and cook on high for 15 minutes until tender and heated through.