Preheat the oven to 350 degrees
Begin with the dried guajillo chilies - I find these at my favorite local Mexican market (El Burrito Mercado) or in the grocery store ethnic foods aisle - if you are using chili powder instead of dried chilies, skip to step 7
Choose 3 large or 4 small dried guajillo chilies
Using kitchen scissors or a sharp knife, cut the top & bottom off the chilies and cut them down the middle
Remove the seeds & ribs from the chilies and cut them in half
Spread the chilies on a baking sheet and bake until toasted and blistered - only about 2 minutes - check them often
Combine the tomatoes, garlic, cumin, salt & pepper and 2 of the toasted chilies halves (or 1tbsp of the chili powder) in a blender
Blend until smooth and taste - add more toasted chilies (or chili powder) a little at a time and blend until you get to a nice spice level for you. I like it to have a good kick so I usually use all of the toasted chilies
Heat the olive oil in a large saucepan until hot and remove from the heat - if using chili powder, skip to step 12
Place a mesh strainer over the pan and pour the sauce into the strainer from the blender
Using a large spoon, press the sauce through the strainer to remove the pieces of chili skin. Remove the strainer
Cook the sauce over medium heat, stirring often, until the sauce reduces slightly and is the consistency of tomato paste - about 6-8 minutes
Add the chicken broth, bring to a boil, reduce the heat and simmer for 10 minutes so the flavors meld
While the sauce is simmering, place the tortillas on a baking sheet, spray with cooking spray or brush with oil and cook until soft & pliable - about 3 minutes
Spread a 1/2 cup of enchilada sauce in the bottom of a 9x13 pan
In a large bowl, combine the shredded chicken, a cup or so of the enchilada sauce and 1 cup of the cheese
Top each tortilla with a generous portion of the chicken mixture
Roll up the enchiladas and place them into the 9x13 pan - I somehow always end up with 13
Spoon the remaining enchilada sauce over the pan
Sprinkle the other cup of cheese on top and either cover and refrigerate the pan for later or put in the oven uncovered
Bake at 350 degrees for 20-25 minutes or until hot and bubbling.
Serve with cilantro and sour cream and your favorite rice, salad or chips