Very tasty recipe, even when I scaled it up to 24 servings so that we could feed the horde here at our ranchero. Only thing was that the Gran Luchito products are made in London and primarily distributed in the EU. I found some of them on Amazon, but at a totally ridiculous price. And we used chuck roast in place of the rump roast, since that's easier to get by name although they are similar.
Luckily, since we have a commercial kitchen on our property for my wife's small batch salsa and hot sauce business, I was able to contact her suppliers who gave us recommendations for substitutes.
For the Tomatilo sauce, we used green enchilada sauce in 15 ounce cans, 1 per sachet. For the Cantina beans, we used 15 ounce cans of Bush's Seasoned Black Beans, and we added some extra cumin and coriander to the beans. Same ratio for the sachets.
Everyone loved it, and we had NO leftovers. That makes it a keeper for us.