Place the unpeeled onion and garlic cloves on a baking sheet and cover with aluminum foil.
Bake for 30 to 40 minutes or until soft.
Allow to cool and remove peels.
Heat a dry skillet on med/high and toast the chilies on both sides.
Pour the hot water into a medium bowl and add the toasted chilies.
Place another bowl or plate on top of the chilies to weight them down.
Allow the chilies to re-hydrate for 30 minutes.
Remove the chilies and reserve the water.
Place the chilies, sesame seeds, oregano, cinnamon, clove, cumin, ground pepper and dates in a food processor along with one cup of the reserved chili soaking liquid.
Pulse and puree the mixture until everything is as smooth as possible.
Strain the mixture through a fine mesh wire sieve and discard the solids.
Place the strained mixture in a large Dutch oven or pot.
Place the cooled roasted onion and garlic in the food processor with the tomato sauce and puree until smooth.
Add the onion mixture to the pot with the chili mixture.
Place over med/high heat and stir occasionally.
Cook until the mixture becomes a thick paste.
Add the chicken stock, chocolate and bread crumbs and cook on med/low for 30 minutes.
Add the tablespoon of sugar and apple cider vinegar if needed and salt to taste.
Server over tacos, enchiladas or other Mexican dish.