Add the tablespoon of oil and the first four ingredients. Saute the vegetables until tender and aromatic, about 5 minutes.
Leaving the flame on high, add the tomato paste. Using a spatula, move the tomato paste around vigorously to avoid sticking. Cook the tomato paste around 2 minutes and remove from the heat. (This is caramelizing the tomato paste, you want that, oh yes you do!)
Add the three kinds of beans, the stock, and seasonings. Return to the stove top using medium heat and let simmer for at least an hour until it is the consistency you prefer. (I prefer for most of the liquid to be reduced, but if you want a ’soup’ier chili then let simmer only 45 minutes.)
I like to let my chili sit in the pot and cool down for an hour or two. The longer it sits together the better the flavors will taste together. You can easily reheat the chili on the stove top or microwave.