In a 5 or 6 quart kettle, I use my cast iron dutch oven, cook onions and green pepper over medium high heat using the stock until the onions are golden and pepper is soft. Add mustard seeds and cook stirring for a couple of minutes. Add chili powder, cumin seeds, cocoa, cinnamon, tomatoes undrained, beans and their liquid and tomatoe paste. Reduce heat and simmer rapidly uncovered for about 40 minutes or until most of the liquid has cooked away and chili is thickened; stir frequently to prevent scorching. Season with salt to taste and serve with Pink Onions (recipe below)