Toast the seeds briefly on a dry sauté pan, being careful not to burn them. Cool completely, then grind together with peppercorns and cumin as finely as possible. Put the ground ingredients into a bowl, stir in a half-cup of broth to form a smooth sauce. Set aside.
Blend or process remaining ingredients into a smooth puree.
Heat oil in a large saucepan, add the blended vegetables and herbs, and cook over medium-high heat until the sauce reduces (about 10 minutes), stirring occasionally. Lower the flame and gradually stir in the pumpkin-seed mixture. Don’t let the mixture boil! Gradually add the rest of the reserved broth. Heat thoroughly over a very low flame, stirring and scraping, for 20 minutes.
Add meat or vegetables, adjust salt, and cook another 10 minutes, or until veggies are cooked. Serve hot, preferably with corn tortillas.