Heat a cast-iron griddle or comal over high. Pan-roast the whole poblano peppers until all sides are blackened and blistered, about 10 minutes. Make sure to rotate the peppers throughout cooking.
Broil
Turn the oven onto broil and line a baking sheet with aluminum foil. Spread the whole poblano peppers out evenly and broil for 10-15 minutes, flipping halfway.
Flame roast
Turn a gas stove burner onto high. Using tongs, roast the whole poblano peppers directly over the flame, turning throughout, until all sides are blackened, about 2-3 minutes per side.
Steam & peel
Once they are roasted, transfer the poblanos to a Ziplock bag or bowl with plastic wrap over top to help loosen the skins. Let them steam for 5-10 minutes, then peel the skins off.
Open the peppers up and remove the seeds and veins, then slice them into thin strips or use them as-is for sauces, etc. Wash your hands well after handling them or wear gloves.
Notes
Nutritional information is a rough estimate and should not be taken as health advice.