Prepare the Chicken:
If you haven’t already, cook the chicken by either boiling, baking, or using a rotisserie chicken. Shred the chicken with two forks and set it aside.
Combine the Ingredients:
In a large bowl, combine the shredded chicken, cream cheese, ranch dressing, buffalo sauce, garlic powder, butter, and half of the shredded cheddar and mozzarella cheese. Mix everything until smooth and well-combined.
Transfer to Slow Cooker:
Pour the mixture into the slow cooker and spread it out evenly.
Cook:
Cover the slow cooker and cook on low for 2–3 hours, or until the dip is hot and the cheese is fully melted. Stir once or twice during the cooking process to ensure everything blends together.
Add Cheese:
Once the dip is heated through, sprinkle the remaining cheddar and mozzarella cheese on top. Cover again and cook for an additional 10–15 minutes, until the cheese is melted and bubbly.
Serve:
Stir the dip to combine the melted cheese and serve warm with chips, crackers, or cut veggies for dipping.