Preheat oven to 300°F.  Separate 4 cloves from a head of garlic, but do not peel.  Place the cloves on a square of aluminum foil and drizzle with olive oil. Season generously with salt & pepper.  Close the foil to wrap tightly and place packet on baking tray.

Roast in oven for 45 to 60 minutes, until very soft.  Squeeze the pulp from the skins, discarding the skins.

Preheat oven to 375°F.  Brush the peppers on all sides with olive oil.  Season generously with salt & pepper.  Place in the oven on a rimmed baking sheet.  Rotate until charred on all sides, about 20 minutes.

Remove from the oven.  Immediately place the roasted peppers in a bowl and cover tightly with plastic wrap.  Let sit for 15 minutes to allow the skin to loosen.  Peel, halve, seed and roughly chop peppers.

Empty contents of a can of chipotles in adobo sauce into a food processor and blend until smooth.  Chile puree can be covered and stored in the refrigerator for up to one month because of the vinegar in the adobo sauce.

Depending on the amount needed, remove one or more peppers from a can of chipotles in adobo sauce.  Carefully open and scrape seeds from pepper.  Check for and remove any residual skin left on the pepper.  Mash the pepper with a fork until pureed.

Combine the roasted garlic, roasted red peppers, chile puree, onion, vinegar and mustard in a blender.  Season with salt & pepper.  Blend until smooth.  With the motor running, slowly add the oil and blend until emulsified.  Pour sauce into a bowl.  Cover and refrigerate for up to one day.

NOTE:  Sauce can be stored in freezer until ready to use.