Heat a large skillet over medium heat. Add the oil and the chorizo. Tear the chorizo into chunks before adding. Cook until half cooked, about 4 minutes.
If using cubed frozen hash browns, or fresh cubed potatoes. Cook those separately until cooked through. If using a left over baked potato, cut into cubes and set aside.
Increase the heat to medium high. Add onions and mushrooms, stirring until they are softened. About another 3 - 4 minutes.
Sprinkle in the potatoes and cook until blended and hot.
Season with salt if needed. Chorizo can be salty enough.
Pour mixture into a bowl and serve with warm tortillas. Serve salsa, guacamole, sour cream or hot sauce for garnish.