Preheat oven to 425 degrees.
Brown chorizo over medium-high heat, using a wooden spoon to break up into small pieces. Add minced onions & cook until translucent. You can also add minced garlic and/or jalapeno. Drain off excess fat, & spread into the bottom of a medium sized casserole dish.
Cover the chorizo with the shredded cheese. Bake for 6-8 minutes, until hot and bubbly and all the cheese is melted through.
Serve hot with tortilla chips or warm tortillas.