Heat 1 tablespoon of olive oil in a medium saucepan over medium heat. Add 1 diced onion and sauté until soft and translucent, about 5 minutes. Next, add 2 minced garlic cloves and 1 diced jalapeño, cooking for an additional 2 minutes until fragrant.

Reduce the heat to low, then gradually stir in 8 ounces each of shredded white American cheese and white cheddar cheese. Pour in 1 cup of half-and-half, stirring continuously for about 5-7 minutes until the cheese is fully melted and the mixture is smooth and creamy.

Once fully melted, add 1 teaspoon of ground cumin and 1 teaspoon of chili powder to the cheese mixture. Stir well to combine, and taste to adjust seasoning with salt and pepper. Transfer the dip into a serving bowl and garnish with cilantro or diced jalapeños. Serve warm with tortilla chips.