Pre-heat the broiler to high.
With the oven door ajar to allow steam to escape, broil the poblanos until charred all over. Place the poblano peppers in a bowl, cover with plastic wrap and let cool. Peel, seed and roughly chop.
Melt the butter in a large skillet over medium-high heat. Add the onion, garlic and cumin and season with salt and pepper. Cook until the onion is translucent, 8-10 minutes.
Add the poblanos, then whisk in the flour and cook for 1-2 minutes. Add the stock and let thicken.
Transfer to a food processor; add the cilantro and puree. Transfer to a pot, add the cream and let thicken to coat a spoon.
Freeze flat in a gallon-size bag or in small sandwich-size bags for smaller servings.
Serve over chicken, pork or steak.