In a small bowl combine 1/2 cup mayonnaise, 2 tbsp finely chopped parsley, 1 tsp chopped oregano (or 1 tsp dried), 1 minced garlic clove, 1 tsp red wine vinegar, 1 tsp olive oil, 1/4 tsp red pepper flakes, 1/4 tsp salt and 1/8 tsp black pepper. Stir until homogenous. Taste and adjust salt or acidity. Refrigerate while you prepare the rest so flavors meld.

Prepare the side (oven fries)

Oven fries

Preheat oven to 425°F (220°C). If using whole potatoes, cut into 1/4- to 1/2-inch sticks. Toss potatoes with 1 tbsp olive oil and 1/2 tsp salt on a rimmed baking sheet in a single layer. Bake for 25–35 minutes, turning once, until golden and crisp. Keep warm in low oven (200°F/95°C) while you cook the sausages.

Cook sausages

Heat a skillet or grill to medium-high. If using a skillet, add a light drizzle of oil just to prevent sticking. Prick each chorizo lightly with a fork in a few places to prevent bursting. Cook the sausages, turning occasionally, until browned and cooked through to an internal temperature of 160°F (71°C), about 10–12 minutes depending on thickness. If grilling, cook over medium heat, turning until evenly charred and cooked. Rest 3 minutes off heat.

Prep bread and toppings

While sausages cook, halve the baguette lengthwise (do not cut all the way through if you prefer hinge style) and lightly toast the cut sides on the grill or in a toaster oven until golden, about 1–2 minutes. Slice tomato into 1/4-inch rounds and thinly slice the red onion if using. Tear or place 1 lettuce leaf per sandwich portion (you will have 4 leaves for 4 sandwiches).

Assemble choripán

Slice each cooked chorizo in half lengthwise (optional) or leave whole and place into the toasted baguette. Spread 1 to 1 1/2 tbsp of chimichurri-style mayo on both cut sides of the bread. Add lettuce, 2–3 tomato slices and a few onion rings per sandwich. Place the sausage(s) into the bread and close. If desired, squeeze a lemon wedge over the sausage for brightness. Cut into 4 portions and serve immediately with oven fries.

Serving & finishing touches

Plate each choripán with a portion of fries. Offer extra chimichurri-style mayo and lemon wedges on the side. Recommend serving hot so the bread is crisp and sausage juicy.