Vegan Chili

In the insert of a slow cooker (or a Dutch oven or large pot), heat the olive oil over medium-low heat. Add the onions, garlic, and mushrooms, and season with soy sauce. Cook until the onions and mushrooms have wilted.
Add cumin, paprika, cayenne pepper, oregano and stir for 30 seconds to coat the mushrooms and give the spices a chance to become fragrant.
Stir in the tomato paste, diced tomatoes, vegetable broth, beans, celery, and sugar. Bring to a boil, then lower heat to a simmer. The longer it cooks, the better it tastes (and I do believe it tastes better the next day). If you are using a slow cooker, transfer to a slow cooker and let it bubble for 4 hours on high or 8 hours on low. If cooking on the stove, cover and cook slowly and taste often, adjusting seasonings as necessary with salt and pepper, for at least 1 hour, stirring occasionally.
Use an immersion blender to blend some (not all) of the chili for a thicker texture.
When serving, garnish with green onions, vegan sour cream, cilantro, jalapenos, etc.