Scoop the potato into a microwave-safe bowl, cover with plastic wrap, poke a few holes in the top and microwave on high for 3 minutes.
In a large skillet (preferably non-stick), set over medium heat, lay the chorizo and onions. Cook, stirring frequently and breaking up clumps, until the fat renders, the sausage looks cooked, and the onions are translucent, about 6 minutes.
In a blender, combine the tomatoes, chipotle chiles and canning liquid, and blend until coarsely pureed. Pour the mixture into the pan with the chorizo and onions, on medium heat for about 5-10 minutes until the tomato mixture has cooked down to look like tomato paste. Add the salt, oregano, pulled chicken, potatoes and ½ cup of water to give the mixture a saucy consistency. Heat thoroughly.
Serve the mixture in a bowl with warm tortillas on the side. Let guests add avocado, cheese and cilantro to taste.