1. Start by dicing the chorizo into small chunks.
2. Heat a skillet over medium heat and add the chorizo. Fry until it becomes crispy and releases its flavorful oils. Set aside for assembly.
3. In the same skillet, add a bit of oil, then toss in diced onion, jalapeño, and minced garlic. Cook until softened and lightly browned. Combine with the fried chorizo.
4. Butter one side of each slice of bread generously.
5. Place the buttered side of the bread down on a clean surface.
6. Layer a combination of Monterey Jack, Mozzarella, and any additional cheese you prefer, along with the chorizo mixture.
7. Add optional avocado slices for extra creaminess.
8. Preheat a skillet or grill to medium heat.
9. Place the assembled sandwich onto the heated surface, butter-side down.
10. Cook until the bread turns golden and the cheese begins to melt.
11. Carefully flip the sandwich and cook the other side until crispy and the cheese is gooey and fully melted.
12. Just before finishing, spread a layer of chipotle mayo on the inside of the upper bread slice.
13. Remove the sandwich from the skillet, cut in half if desired, and serve immediately while hot. Enjoy your Chorizo Grilled Cheese!