Rinse the poblanos and roast them in the oven at 400F. Give them a flip after 15 minutes. They'll be mostly roasted in another 10-15 minutes, so 25-30 minutes total roasting time in the oven.
Add 3 tablespoons butter to a saucepan on medium heat. Roughly chop an onion and add it to the saucepan, cooking for 5-7 minutes or until softened. Mince 4 garlic cloves and add to the onion, cooking for a minute or so.
Add 3 tablespoons flour to the onion mixture and combine well. Add 4 cups of stock along with 2 teaspoons Mexican oregano (optional), a pinch of cumin (optional), ½ teaspoon salt, and freshly cracked black pepper. Stir well. Simmer for 7-8 minutes.
Once the poblano peppers have cooled a bit, pull off as much skin as you can but don't worry about getting rid of all of it. Then de-stem and de-seed the poblanos. Roughly chop the poblano pieces and add them to the saucepan.
Cook until everything is at a uniform temp and then combine the mixture in a blender. Be sure to use caution when blending hot liquids -- I usually just hold a paper towel over any openings just in case you get a geyser.
Return mixture to the saucepan and simmer for 5-10 minutes. Salt to taste. I added another ¼ teaspoon of salt but keep in mind the salt level will depend on which stock you use.
Serve immediately but don't forget to garnish! I used Crema, finely chopped cilantro stems, freshly ground pepper, and a couple dashes of Valentina hot sauce.
The acidity of the hot sauce pairs well with the poblanos so feel free to re-garnish once you make your way through the top layer. Other options for acidity: lemon/lime juice or vinegars.
Store leftovers in an airtight container in the fridge.