Add the oil to a pan along with the onions, garlic, carrots and mushrooms
Cook on a medium/high heat for around 5 to 7 minutes until the onions soften and the mushrooms start to reduce in size
Sprinkle over the cornflour and give the veg a stir to mix in the cornflour evenly
Deglaze the pot with the balsamic vinegar (or red wine)
Add the tomato puree, tamari, sweetener and mustard to the pan along with 500ml (2 cups) of boiling water
Bring the gravy to a boil and then turn down to a gentle simmer for around 12 minutes to allow the sauce to thicken and all of the flavours to infuse
Serve the gravy according to your preference. You can either strain the gravy and serve as a smooth gravy sauce, serve the gravy as it is as a rustic gravy or blend into a thick sauce