Add your fluids and butter to a microwave/oven safe bowl as per manufacturers directions. However, cut back slightly on the fluids [milk or water-whatever the box calls for] since the Velvetta cheese will create additional fluid when melted.
Add your Velvetta cubes, garlic, onion powder and 1/4 cup chives and microwave until melted.
Add your powdered cheese and whisk everything together then add your dried potatoes.
Bake as per manufacturers directions. Usually at 400° for 35-40 minutes.
When almost baked, pull out pan and sprinkle potatoes with your 4 tbs fresh chives and shredded Velvetta and bake for an additional 10 minutes or until cheese is fully melted.
Sprinkle pre-shredded cheese on top if you'd like.