Heat the oil and once hot add the onion with a pinch of salt and sauté for a few minutes. Next add the cabbage, mix well and cover and cook until cabbage is soft.
Make the sauce while the cabbage is cooking by blending the garlic, tomatoes, chipotle pepper and a little bit of salt until completely smooth. You may want to add one of the chipotles at a time and a bit of the abodo sauce so that you can keep taste testing it to make sure it doesn't get too spicy for you.
Once the cabbage is cooked, add the shredded carrot and pour in the salsa. Give the mix a good stir to well combine, cover and simmer for about 15 to 20 minutes or until ready to serve. Taste and if needed add more salt.
Assemble each tostada by smearing some refried beans on it then adding a generous layer of the cooked tinga, then drizzle with sour cream and cheese if using, lastly add a couple of slices of radishes and avocado. Server right away as the tostadas will get soggy and crack. Leftover cooked tinga can be stored in the fridge for several days or frozen for several months.
* If you want to make these tostadas 100% vegan use my almond crema recipe & either omit the cheese or use a vegan substitute. Find the crema recipe here, Vegan Crema Fresca*Want to make your own refried beans? Here's my recipe, Vegan Refried Beans * You can buy the chipotle peppers in adobo sauce just about anywhere, or you can get them online here http://amzn.to/2wqbAMa* The tostadas too can be purchased in supermarkets or online here http://amzn.to/2iPe5mr (I used baked ones)