In large, heavy skillet saute onion over moderately high heat until golden brown.
In motar, crush coriander seeds and aniseed or grind in a spice grinder. Stir into onion mixture with chili powder, sugar, cinnamon and cloves. Cook mixture over medium heat, stirring, for 1 minute. Stir in cocoa powder, peanut butter, 2 cups of broth, tomatoes, raisins, garlic paste and salt, to taste and simmer sauce loosely covered, stirring occasionally, for 20 minutes. Take the sauce off the heat and let cool while preparing the chicken legs.
Pat legs dry, season with salt and pepper. On oiled rack of a broiler pan, broil skin side up for approximately 10 minutes, turn and broil other side for approximately 10 minutes or until golden brown.
In blender or food processor puree the sauce in batches, adding remaining broth as necessary to thin.
Transfer sauce to skillet, add legs, and simmer mixture loosely covered for 30 minutes.
Serve legs with mole sauce over rice. Sprinkle with sesame seeds.