Preheat oven broiler. Place poblano peppers on a lined baking sheet and broil for 5-8 minutes on the top rack until skin blackens and begins to crack. Turn peppers over and broil an additional 5 minutes.
Next, place roasted peppers into an airtight container for 5 minutes to loosen the skin (it needs to be peeled before blending).
Remove charred skin from pepper and discard seeds, skin and stems. Slice the poblano pepper in half.
Add half of the poblano pepper and all other ingredients to a high speed blender. *Note: I recommend starting with half so that you can add more depending on the spice level.
Blend dressing until completely smooth, stopping to scrape down the sides as needed. Taste test the dressing to determine spice level since spiciness greatly varies in peppers. If you’d like it spicier, add the remaining ½ of pepper and blend until smooth.
Add additional salt and pepper to taste, as well as any additional milk (I recommend 1 tbsp at a time) to thin the dressing as desired.