Grill the chorizos in the grill, either outside or inside. I sometimes use a small electric oven. If they start to sputter, prick them a few times with a fork to release the fat.
If using the stove grill or oven, it should take at least 20 minutes at a medium heat. Let it cook thoroughly, you don’t want raw chorizo. Open it, butterfly style, and sear it for a few minutes. You can also leave them whole, but I like it to be charred as much as possible, that's why I butterfly it.
I like to warm the bread, either by popping them a few minutes in the oven or on the grill, but it’s not really necessary if you like the bread and it’s very fresh.
Open the bread in two, add some salsa, put half or the whole butterflied chorizo on top (depending on the size of the bread), some chimichurri and more salsa.
Top with the remaining bread.
For the salsa criolla:
Put the diced onion, tomato and red pepper in a bowl.
Add vinegar, salt, olive oil and black pepper to taste, adjusting it to your palate.
Add chopped parsley. Mix well.
Notes
Type of chorizo sausage: use mixed sausages with pork and beef, ideally 70-30%.Use crusty French bread, not soft buns. As an appetizer, use small breads and add half a chorizo per sandwich.If you barbecue them outside, they should take 20-30 minutes to be done, half on each side, so that some fat is rendered and the skin is crisp. Pierce them a few times with a fork before grilling so they don't burst in the grill.Butterfly chorizos: when they are almost done, open in half lengthwise, and grill them a little longer, cut side down.