Melt 1 tablespoon butter in a saucepan over medium heat
Add 1 small diced onion and cook until soft
Add 1 minced garlic clove and cook for 30 seconds
Stir in 1 tablespoon flour and cook for 1 minute
Slowly whisk in 1 cup milk until smooth
Add 2 cups shredded cheese and stir until melted
Mix in 1 can diced green chiles
Add salt, cumin, and chili powder to taste
Stir until creamy and smooth
Serve warm with tortilla chips