Combine chimichurri ingredients in a bowl, cover and place into the refrigerator until ready to use.
Preheat grill for medium heat.
Place sausages on the grill and cook for 3 minutes, flip over, and cook for another 3 minutes. Remove sausages from the grill and place onto a cutting board. Using tongs to steady the sausage, cut each one ¾ of the way through, lengthwise. Do not cut all the way through. Return to the grill cut side down, and cook for another 3-4 minutes, until done.
Remove cooked sausages from the grill and quickly warm bread if desired.
To plate choripan: Place cooked chorizo onto warmed baguette or hoagie roll. Top with 2 tablespoons (or more) chimichurri. Top with shredded lettuce and diced tomatoes, and serve.