Turn the oven to broil, and put the oven rack on the bottom. Grease a 9X12 casserole dish.
Cook pasta in a large pot of boiling, salted water until aldente. Drain, set aside.
In a small saute pan, add the chorizo and cook for 5-7 minutes. Set aside or keep on low.
Melt two tablespoons butter in the same pot over a medium-heat. Whisk in flour, cook one minute.
Slowly whisk in milk. Bring to a boil and reduce to a simmer until slightly thickened, about 5-7 minutes. Turn heat down to low.
In a small sauté pan, melt the remaining 4 tablespoons butter over a medium heat. Add breadcrumbs, stir until coated.
Add pasta back to pot with the milk. Slowly add in cheeses, stirring to combine as you go. Once the mixture is creamy and all the cheese is added, throw in chopped poblano peppers and chorizo.
Season to taste with salt and pepper.
Pour mixture into prepared pan and sprinkle with panko. Broil just until the panko is golden brown.