Step 1: In a medium saucepan, combine heavy cream, sour cream, and mayonnaise over medium heat.
Step 2: Stir constantly until the mixture is warm and well combined, about 3-5 minutes.
Step 3: Gradually add shredded sharp cheddar and Monterey Jack cheeses, stirring until melted and smooth.
Step 4: Reduce heat to low and stir in garlic powder, onion powder, and cayenne pepper (if using).
Step 5: Season with salt and black pepper to taste, and continue stirring for another 2-3 minutes until fully blended.
Step 6: Remove from heat and transfer to a serving bowl. Garnish with chopped chives or green onions if desired.
Step 7: Serve warm with tortilla chips, bread, or vegetable sticks.