Prep the chicken: Shred cooked chicken into bite-size pieces. Pat dry if it’s very moist so the dip doesn’t get watery.
Soften the base: In a bowl, combine cream cheese, hot sauce, ranch, garlic powder, onion powder, and butter if using.
Stir until mostly smooth.
Load the crockpot: Add the chicken and the cream cheese mixture to a 2–4 quart slow cooker. Stir in cheddar and mozzarella.
Cook low and slow: Cover and cook on Low for 2–3 hours, or on High for 1–1.5 hours, until hot and melty. Stir halfway to prevent hot spots.
Finish and season: Stir well.
Taste and add salt, pepper, or more hot sauce as needed. Fold in blue cheese or sprinkle on top.
Serve warm: Switch to Warm and garnish with green onions or parsley. Set out with your favorite dippers.