Preheat oven to 400 degrees.
Place the diced onion, tomatoes, garlic powder, chicken broth and the whole chicken breasts in a large saucepan. Simmer for 30 minutes until the chicken breasts are tender enough to easily shred.
Let the mixture cool. Remove the chicken breasts and shred, keep the remaining ingredients in the pot.
Blend the remaining remaining mixture until smooth.
Pour the mixture into a saucepan, heat up to a gentle simmer. Then add in all the seasonings until well blended. Add more salt, if needed.
Spread ½ cup of enchilada sauce onto the bottom of a 13x9 inch baking pan.
Spread about a ½ teaspoon enchilada sauce onto the middle of each of 12 corn tortillas.
Place 1 tablespoon of shredded chicken on top of the enchilada sauce followed by a sprinkling of both cheeses.
Roll the corn tortilla up and place in the 13x9 inch baking pan. Repeat for the remaining 11 tortillas.
Top the rolled enchiladas with the remaining enchilada sauce and both shredded cheeses.
Bake at 180 C, uncovered for about 10 minutes or until bubbly.
