Using a deep frying pan, melt the butter over medium-high heat. Once melted, add the diced onions and diced jalapenos. Cook over medium-high heat for 5-6 minutes, or until onions begin to turn soft. Add diced garlic and cook for 2 more minutes, stirring often.

Whisk the flour and cumin into the pan and cook for about 45 seconds, stirring constantly.

Add the milk and cubed cheeses. Reduce heat to medium-low and cook for 8-10 minutes, stirring occasionally, or until cheese has completely melted.

Remove from heat and stir in the canned diced tomatoes, canned diced chilies, cilantro and sour cream; stir until well combined.

Transfer mixture to a serving bowl; serve hot with tortilla chips.