In a small bowl, add your chillies, ½ red onion, and garlic. Then cover with 200ml of boiling water. Leave for 15 minutes.
Remove the chillies, onion, and garlic from the water and place in a blender with 50ml of the chilli water. Blend until smooth (add in more water if it's too thick). Set it aside in a small Tupperware.
Grab yourself a frying pan and place it on medium heat. Add in some vegetable oil, then add in ½ onion, chorizo, boiled potatoes, cumin, oregano, and paprika. Fry for 10 minutes on medium heat until well combined.
In a bowl, combine your grated Mexicana Cheese and sour cream.
Place down the bottom of your sliced roll into the centre of some baking paper or tin foil. Spoon on some of the chorizo and potato filling, lettuce, avocado, cheese mixture, and the top of the sliced roll...wrap it up, and then it's ready for your picnic! Don't forget to take the dipping sauce in a separate little Tupperware!