Tacos are best with freshly made tortillas. If you're lucky enough to have a tortilla factory near you, buy them the same day you're going to make the tacos.
Bring a large pot of water to boil (or use a 2-part steamer with pot and basket).
Cook chorizo in a medium nonstick frying pan over medium, breaking it up with a wooden spoon, until it is lightly browned and cooked through.
When water is boiling, set a colander over it so that it doesn't touch the water, set the tortillas in 2 stacks into the colander, and cover them lightly with foil (or set them into the basket of the steamer). Steam for 3–4 minutes.
Make 12 tacos, each with a base of 2 tortillas, by dividing chorizo equally between them, using a slotted spoon. Sprinkle minced onion and then chopped cilantro over each serving of chorizo, dividing them evenly. Divide cheese equally between tacos, if using. Place 1 lime wedge alongside or on top of each taco.