Another approach to creating a salsa aside from those based on tomato, tomatillo or vinegar, all of which we have seen already, is to use toasted dried chiles blended with water or stock as the base and thicken the resulting mixture with a roux made of lard and masa harina. This type of salsa is generally used to braise meat as opposed to being used as a condiment.
There are a lot of variations here. Different types of dried chiles can be used, the roux can be made from masa and lard, from flour and butter, a slurry of flour can be used or the roux omitted altogether and the salsa allowed to thicken naturally.
Toasting the Chiles and the Garlic
I used a combination of chile ancho, chile passila and small chile de arbol. The ancho has a deep raisin taste, the chile de arbol resembles a dried thai birds eye chile, they round out the flavour of the passila, giving additional depth and heat.
The easiest way to toast them is on top of a hot comal. You can remove the stem, split them down the middle, open them out, remove the seeds and membrane and then toast them briefly, pushing them down with a spatula for a few moments on each side until they are fragrant but not burnt. Alternately you can lay the unopened on the comal, turning regularly and remove the stem, seeds and membranes afterwards.
I used roughly 3 anchos, a half dozen passila and another half dozen chile de arbol. After toasting the chiles are placed in a bowl of hot water to soak, weighted under a plate to keep them submerged if necessary.
As the chiles are toasting you also need to toast 3 or 4 cloves of garlic on the comal in their skins until soft.
Blending the Salsa
There a couple of divergences here. Some authors suggest that the soaking liquid is too astringent to be added to the blender. Some also suggest adding water while others use chicken stock.
Personally I don't find the soaking liquid to be a problem, however I would not add all of it to the blender lest the salsa be too loose, and I would certainly use chicken broth if some was available. Perhaps I'll just sit on the fence and suggest 3/4 of a cup of each.
Along with the liquid and the soaked chiles you will also need to add about 1/2 teaspoon each of oregano, cumin and salt. Blend everything to a fine purée.
Cooking the pork.
For the carne part of the dish I used leg of pork cut into 1cm dice. Pork shoulder would also be fine, in fact any meat which benefits from long slow moist cooking would work well.
The neat needs to be browned on all sides, when the meat is coloured remove from the pan. In a clean pot make a roux from a tablespoon of lard and a tablespoon of masa, allow to cook through and then add the salsa, straining it through a sieve to catch any pieces of chile or cumin that didn't blend fully, then add the meat and any juices to the salsa.
The whole thing is simmered slowly until the meat is tender - at least and hour.
The meat and salsa freezes well. It makes a beautiful taco, either with the meat left in cubes or pressed lightly with a masher while reheating so that is falls into strips and drinks up the salsa.