In a large saucepan oven over medium high heat cook chorizo until fully cooked. (if using)

With a slotted spoon remove cooked chorizo and place on paper lined plate to drain.

Wipe saucepan clean with a paper towel, return pan to medium high heat and add butter.

Add onions and poblano and cook until translucent, about 5 minutes.

Add flour to vegetables and stir to combine. Cook an additional 45 seconds.

Add the milk and continue to cook on medium, whisking until sauce is thick, about five minutes.

Reduce heat and slowly begin adding cheese to sauce, stir to combine until the cheese melts and add repeat until all cheese is added.

Stir in tomatoes and cooked chorizo.

Season with salt and pepper. Garnish with cilantro.

If queso thickens add milk as needed until desired consistency.

Serve warm with tortilla chips.