Something magical happens when you roast chiles. And don't be put off by having to roast them - it's simple and you'll be so glad you did.
1 1/2 pounds poblano chilies (about 5 or 6)
1 tablespoon olive oil
1 tablespoon butter
1 small white or yellow onion, diced
2 cloves garlic clove, minced
5 cups chicken broth or vegetable broth
1 small bunch cilantro, no stems
Kosher salt & fresh ground pepper
1/2 - 1 teaspoon cayenne pepper
Place chilies on baking sheet and broil until blackened all the way around - you'll have to turn them a couple times. Or you could put them over your stove's open top and keep turning until blackened all around.
Put in a paper bag and seal for 10 minutes to steam.
Peel off blackened skin, remove stem and seeds and rough chop - set aside.
Heat oil and butter in large deep skillet, cook onions over medium heat about 10 minutes until softened.
Add chilies and garlic, stir until fragrant and put in a blender.
Add 3 cups of the broth, cilantro, cayenne and season with salt & pepper.
Blend until smooth, put back in the pot and add remaining 2 cups of broth. Mix well, let thicken slightly and serve.