Preheat oven to 400 degrees
Put rinsed poblanos on a baking tray and roast for 30 minutes, 15 on each side
Take poblanos out of the oven and let them cool.
While they are cooling, add 3 Tbsp of butter to a large pan on medium heat.
Add chopped onion to the pan, sautéing 5-7 minutes.
Add minced garlic to onions, sautéing 1-2 minutes
Add 4 cups of stock along with salt and pepper to taste. Stir well.
Bring mixture to a simmer and cook for 8-10 minutes.
Once the poblano peppers have cooled, pull off the stem and as much skin as you can.
Then, de-seed the poblanos, scraping the insides with a knife.
Roughly chop the poblanos and add them to the saucepan.
Using your immersion blender, purée soup, until creamy.
Serve with sour cream and/or chopped cilantro.