This a process but I will take you through it step by step. First you need a bunch of dried red chilies. YOu can buy them at any grocery store in the Mexican food section. They come in a plastic package next to the corn husks you can buy for making tamales. They are dark red in color. YOu want to wash them, take the stems off and shake out as much of the seeds as you can. Then place them in a large pot with the onion and garlic. Bring it to a boil and boil for 30 minutes or until the chilies are tender like this:
As you boil them they lighten in color. Drain all the water off of them. Then place them in a blender in batches adding fresh warm water from the tap until it is smooth and the desired consistency you want. Here are some chilies in the blender with water before blending them up:
I don't measure the water because I just add more until it is the consistency that I want. I usually almost cover the chilies with water. Sometimes I have to add more. Blend really well. Then if you have a mesh strainer(it works better than a regular plastic one) dump the pureed chilies into the strainer that has a pot under it to catch the sauce like so:
Stir around with the spoon till most of the sauce goes through the strainer into the pot. Straining it gets the rest of the seeds out of the sauce and some of the hard skins that don't blend well. You will have leftover mushy stuff that won't go through the strainer and throw that away. Continues this process until all the chilies are pureed and have been strained. The sauce in the pot should look like this when you are done straining it:
Place on the stove add 3 tsp chicken bouillon and salt to taste. It usually takes a lot of salt you will just have to taste until you have the right saltyness for your taste buds. bring it to a boil. Turn the heat down and simmer for 30 minutes to an hour. Then use the sauce however you like. For enchiladas or to have a smothered burrito.
Believe me it is worth the effort!!!