Begin by bringing a pot of water to a gentle boil over medium-high heat. Carefully add the boneless, skinless chicken breasts and allow them to cook for about 15 minutes until they reach an internal temperature of 165°F. Remove the chicken, shred it, and toss with blue cheese dressing.

In a large skillet, melt half of the butter over medium heat. Add the diced yellow onion and celery, sautéing for about 5 minutes until tender. Stir in the minced garlic for another minute.

Pour in the undrained diced tomatoes and chicken broth, bringing the mixture to a boil. Add the penne pasta, cover, and cook for 10-13 minutes, stirring occasionally.

Reduce the heat to low and stir in the buffalo sauce, cream cheese, shredded cheddar, and mozzarella until melted. Mix in the shredded chicken and adjust seasoning with red pepper flakes if desired.

Swirl in the remaining butter, stirring until melted. Serve hot and enjoy!