Yesterday, Lex Petras of Tacos de la Noche explained how his seven sauces became known as the seven deadly sins. Today, he shares a recipe for one of his perfected green sauces. The "Envy" sauce is great with the Al Pastor, said Petras. This sauce, which falls closer to the middle of heat scale, provides an ardent heat that is tempered with a creamy avocado finish.
Peel and halve the tomatillos and place them face down on a sheet tray. Place half an onion and the Serrano peppers on the same tray.
Roast at 400 degrees for 15 to 20 minutes until the tomatillos are soft enough to give a little juice when pushed with your finger. Scrape the roasted tomatillos, onion, and peppers into a blender. Add a little water to the sheet tray to help scrape up the remaining brown bits, and add to the blender.
Puree the mixture, add a bunch of cilantro (Depending on the strength of your blender, you can add both the leaves and the stems or just use the leaves.), and 2 or 3 medium size garlic cloves. Halve and pit an avocado. Scoop the whole avocado into the blender and puree until smooth. Season with salt and pepper to taste.