Remove chorizo from the casings and fry in a medium saute pan until fully cooked. Meanwhile, clean and trim the brussels sprouts and cut them into quarters. When the chorizo is cooked, remove from the pan and set aside. Making sure your pan is hot, drop in the brussels sprouts and stir to coat in the chorizo grease. Cook for about 8 - 10 minutes, tossing occasionally to make sure they don't burn - but not too much or they won't get nicely caramelized which is key to the flavor your looking for. Add the chorizo back to the pan along with the olive oil and cook for another 2 minutes until all of the flavors have blended. Taste and add salt and pepper if you'd like. The chorizo is so flavorful that I found no additional seasoning was needed but that's strictly a matter of personal preference so be sure to taste and adjust before serving.