Any ideas for how to make this without a slow cooker?
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You could certainly make this without slow cooker. Cook the pork and tomatillos on the stovetop, covered, in a large Dutch over for a couple of hours. Then remove the pork, puree the tomatillo sauce, add the dried beans and the pork, and simmer on low, covered, for a few hours until the beans are soft (the timing will depend a lot on the dryness of the beans). You will want to keep an eye on the liquid level and make sure the beans stay submerged.
Another approach would be to braise the pork in a Ditch oven in a low heat (325 degree) oven, then puree the sauce and add the beans and continue cooking in the oven, similar to this recipe: