The secret ingredient to making this recipe taste just like old school chili is lentils. Exploded lentils. If you cook them too hard, they pop open and soften and act as a thickening agent with a result similar to stew.
Red lentils are more delicate than their green or brown counterparts. Customarily, they are cooked at a very gentle simmer. For this recipe, I cook the lentils at an active simmer which causes their fragile skins to rupture and free the starchy inside. This allows them to act as a thickening agent for the chili and adds an authentic texture too.
The balance between the starchy insides of the lentils and the juicy diced tomatoes creates a chili so thick and authentic your omnivore guests will have eaten half a bowl before they realize the dish is meatless.