Heat the oil in a saucepan over medium heat. Sprinkle in the yeast and arrowroot and warm, stirring, until the yeast smells toasty (keep an eye on it - be careful not to burn it). Pour in some rice/soy milk in half-cup lots and keep stirring until the sauce is as thick as you like. Add your chosen vegetable, then mix with a stick blender (immersion blender) until smooth. Serve over baked vegetables, pasta, etc.