In a medium sauce pot over medium heat, melt the butter. When the butter is melted, add the scallion whites (NOT the greens) and cook until soft, stirring occasionally, about 2 minutes.

Turn the heat down to low and add cheese, milk, Sriracha and garlic powder. Cook on low, whisking often, until everything is melted and combined into a thick queso, about 5 minutes. Add all but 1 tablespoon of the scallion greens, and mix everything together again.

Transfer the queso to a bowl and garnish with the remaining scallion greens. Serve immediately, with chips.