Heat the butter and olive oil in a medium saucepan, and add the chopped onions. Stir for a minute.

Add the chopped celery stick and continue to stir for a minute.

Add the chopped mushrooms, stir, and continue to fry for 10 minutes but be careful to not allow the food to burn. keep stirring. Once the pulp has fried, add the curry powder and stir until aromatic.

Add the flour and stir until combined and then gradually add the chicken stock continually stirring to ensure no lumps form until all the stock is added. Simmer for 20 minutes.

Add the Worcestershire sauce and soy sauce.

Using a hand blender, blend the gravy until smooth. Add the pinch of sugar and season with a good amount of ground black pepper. Add salt to taste.

Stir, turn down heat to a minimum and allow to reduce until you have the preferred consistency. Do not allow the gravy to stick to the bottom of the pan.