The sauce was made with finely sliced mushrooms, five finger chillies, some onion gravy powder, vegetable stock, and two squirts of tomato puree.
Stir fry the mushrooms in a separate lidded pan until they squeak. Add half a pint of water. Add the destemmed finger chillies, the gravy powder (two teaspoonfuls), the vegetable stock, and the tomato puree. Stir until the sauce thickens. Add one bay leaf. Turn down the heat and simmer until the burgers are ready.
Once the burgers are cooked, decant to a serving plate along with the fried tomato and onions. Spoon the chilli and mushroom sauce, and serve. Delicious, simple, and warming!