Cook 7 ounces chorizo in a cast iron skillet until fully cooked, about 5 minutes.
Remove the cooked chorizo and set aside.
Add 2 tablespoons olive oil to the skillet and whisk in 2 tablespoons all-purpose flour to make a roux. Cook for 30 seconds, then whisk in 1.5 cups milk.
Continue to cook until the mixture thickens.
Turn the heat to low, and add the chorizo back into the skillet, as well as 10 ounces Oaxaca cheese, ½ cup cilantro, and 4 ounces mexican blend cheese. Mix until well combined.
Top with 4 ounces sharp cheddar cheese.
Place under the broiler until the top is bubbly.
Remove from the oven and allow to cool 5 minutes before serving with 1 cup Pico de Gallo and corn chips.