Char the chiles over a gas burner or under a broiler until blackened on all sides, 6 to 8 minutes. Transfer to a bowl, cover with plastic, and cool. Peel, stem, seed, and finely chop the chiles.
Heat a griddle or large cast-iron skillet over medium-high heat. Cook the tomatillos, turning occasionally, until dark brown in spots, 8 to 10 minutes. Transfer to a plate to cool. Coarsely chop the pepitas in a food processor; transfer to a medium bowl. Without washing the food processor, add the tomatillos and process to the consistency of a chunky sauce. Transfer to the bowl with the pepitas. Stir in the chiles, cilantro, and salt to taste.
Make Ahead Tips
The sauce may be made 3 days ahead, the filling 2 days ahead, and the salsa 1 day ahead. Refrigerate separately. Return the salsa to room temperature for serving.
nutrition information (per serving):
per 1/4 cup;
Photo: Scott Phillips