Add your frozen, boneless, skinless chicken breast in the crockpot. Pour in 2 1/2 cups of warm Alfredo sauce.
Cover and cook on high for 6-8 hours, until fully cooked. Using a fork separate chicken breasts that get stuck together after a couple of hours of cooking, if necessary. Cook on low for 4-6 hours if the chicken is thawed.
Tear or cut the chicken into pieces using a fork.
Add 1 cup Alfredo sauce, minced garlic, pepper and three cheese tortellini. Mix together. Cover and cook on high for 15 minutes until tender.