This is authentic north Mexican chili sauce. It is an excellent sauce to use for slow cooking cubed pork or beef, but it is absolutely the best for enchiladas and Quesadillas!! You’ll be making up recipes to use this sauce on.
1Rinse and split chilies, removing stems and seeds.
2Slightly toast chilies in small batches in a very hot oven for 30 seconds to 1 minute being careful not to burn them.
3Transfer to a heat proof, sealeable container and pour the boiling water over them. Seal the container, opening occasionally to stir. Allow them to soak for 15-20 minutes.
4In a heavy saucepan, cook the onion, garlic, cumin, oregano in the oil over medium heat until onions are translucent, about 2 minutes.
5In a blender, pour chilies and 3/4 of the liquid, along with the onion, garlic, cumin and oregano mixture, setting aside 1/4 of the liquid. Puree thoroughly.
6Strain through a sieve pressing on the solids to get all the sauce out. Throw away the solids. Pour into a heavy skillet and over medium low heat whisk in the reserved liquid and the flour. Allow to simmer, stirring occasionally until reduced to desired consistency, about 30 minutes. Season with salt, sugar and vinegar. This sauce can be made ahead of time, cooled completely and kept in the refrigerator for 10 days.