Sieve the flour into a large bowl. Make a well in the centre, break the eggs into it and add some salt and pepper.

Put the milk and water in a jug, then, using an electric hand whisk, slowly begin to whisk the egg into the flour. As you whisk, the flour around the edges will slowly be incorporated. Then add the liquid gradually, stopping to scrape the flour into the mixture. Whisk until the batter is smooth.

Now place the sliced onions in a bowl, add 1 teaspoon of the oil and the sugar and toss the onions around to get the lightest coating, then spread them on the baking tray.

Next arrange the sausages in the roasting tin, then place the onions on a high shelf in the oven, with the sausages on a lower shelf. After 10 minutes, remove the sausages from the oven but leave the onions in for a further 5 minutes they need to be darkened round the edges. When they are ready, remove them and leave to one side.

Now place the roasting tin containing the sausages on your hob on medium and add a tablespoon of oil. When the tin is very hot and the oil is shimmering immediately pour the batter in all around the sausages. Return the roasting tin to the oven, straightaway, this time on the highest shelf, and cook for 30 minutes.

For the gravy

First add the garlic and mustard powder (if using) to the stock, then add the onions and stock to a saucepan. Now add the second teaspoon of oil, then, using a wooden spoon, stir in the flour.

Then bring it up to simmering point and gently simmer for 5 minutes. Taste to check the seasoning, then serve. When the toad is ready, it should be well-risen, brown and crisp and the centre should look cooked and not too soft in the centre.