Preheat the oven to 425. Place the poblano pepper in a small baking dish (or loaf pan.)
Roast for 15-20 minutes. Then let cool slightly, before seeding and dicing.
In a double boiler or minislow cooker, add the chunks of cheese with the green chilies and grated onion. Stir in the cilantro, ground cumin, followed by the diced poblano pepper, garlic powder and salt, to taste.
Let simmer in the double boiler until completely melted and smooth, or cook on low for 2 hours in the mini slow cooker.
Serve Queso Blanco with corn tortilla chips.