I have a soft spot in my heart for Choripán. I had my first and 50th in its birthplace: Argentina. On the streets of Bariloche whether at an asado in Córdoba or at the local parillas in Buenos Aires, the chorizo and bread were always joined in holy, grease-dripping matrimony.
*Note: Try buying an Argentine chorizo which is spicier and less smoky than Spanish chorizo.
Cook the sausage on a grill or in a pan over medium heat. Just before it's completely cooked, cut it in half length-wise and finish cooking. While the chorizo is cooking, toast the roll for a couple of minutes and fry an egg in a separate pan, if adding.
Place the chorizo on the bread, the egg on the chorizo, and the chimichurri on everything. Buen provecho.