Pipian VerdeSauces that are flavored and thickened with ground pumpkin seeds or sesame seeds are known as pipianes. Tomatillos, fresh green chiles, onion, and herbs add depth to the bright, slightly tart, and nutty flavor of this sauce that's often used with chicken, duck, and seafood.
In a dry skillet toast the pumpkin seeds over medium heat, stirring, until they pop around in the pan, start to brown, and release their aromas, 3 to 4 minutes.
Transfer to a bowl to cool.
When they are cool, grind to a fine powder in a spice grinder.
(I use a coffee grinder reserved for spices.
) Put the ground pumpkin seeds in a blender.
Add the cilantro, tomatillos, serrano chiles, onion, oregano, cumin, salt, and ½ cup of the broth.
Purée as smooth as possible.
If the sauce is too thick, add enough broth to make the mixture the consistency of heavy cream.
Heat the oil in a medium saucepan over medium heat.
Add the sauce and cook, stirring, 2 minutes.
Reduce the heat to low and simmer the sauce, uncovered, stirring frequently, 15 minutes.
Adjust seasoning.
The sauce is ready to use, or store, in a jar or plastic container, cover and refrigerate up to 3 days or freeze up to 3 months.