Cornstarch is my favorite thickener for this vegan stew and should be added before serving. Mix a tablespoon of cornstarch with 1-2 tablespoons of water until it's lump-free, then transfer that to the stew. Increase the heat slightly (it's heat activated), and stir constantly until the stew thickens. Add more if necessary. You could also blend some of the stew for a creamy thickness (method below).