Please note that most recipes for Enchilada sauce call for a thickening agent, and are meant to be used "fresh" and not preserved. It's recommended that you do not include flour, butter, or milk in anything that you're canning. This recipe can be used for preserving or used right away.
Simmer and Blend it Up!
Toss it all in a pot and let it simmer for about 30 minutes, stirring occasionally. Use your immersion blender (or work in small batches in your food processor/blender) until the mixture is smooth, and there are no chunks left. Spend the time to do a good job now, it will save you time and energy later.