In a medium saucepan, add the butter, olive oil, Worcestershire sauce, sugar, salt and pepper. Put on a low heat to melt the butter
Add the sliced onions and garlic, and cook for about 10 minutes until softened, stirring occasionally.
Stir in the flour and cook for another couple of minutes
Turn down the heat as low as it will go and add the stock and thyme. Place a lid on the saucepan and leave for 30 minutes.
Remove the lid and keep on the heat until the gravy has reduced to your preferred consistency.
Notes
The gravy can be made ahead of time and gently reheated before servingTo make vegan / vegetarian, just use oil to cook the onions and swap Worcestershire sauce for a teaspoon of marmite.Nutritional values are based on one of four servings.