Add the cauliflower to a food processor and pulse until it is in small pieces. It should resemble the texture of ground beef. Do the same with the walnuts and set both of them aside.
Cut the bell pepper, onions and celery into large chunks and add it to a food processor along with the garlic and puree until smooth. (I like to use a vegetable peeler to peel the outer layer of the celery to prevent a stringy texture in the chili, but this is optional.)
Heat oil in a pot over medium heat. Add the pureed vegetables and saute for about 5 minutes, until it is translucent and most of the liquid has cooked off.
Add the spices and tomato paste and saute for another minute. Add the flour and cook for one more minute, stirring constantly so it doesn’t burn.
Add the vegetable broth to the pot and whisk until smooth. Then, add the rest of the ingredients and bring it to a simmer. Turn the heat down to low, and cook covered for 30 minutes. Make sure to stir it occasionally so that the bottom doesn’t burn.
Serve immediately with rice and mac salad, or store in the fridge for up to 5 days or freezer for up to 6 months. Enjoy!