To make the batter, sift the flour into a bowl (with a cloth under it to keep it steady), holding the sieve quite high to give the flour a good airing, add some seasoning then make a well in the centre.
Break the egg into it and beat with an electric hand whisk (you can also use a balloon whisk), gradually incorporating the flour, and then gradually add and beat in the milk and water.
When its all in, slide a rubber spatula all around the sides and base of the bowl to get any escaped bits of flour. Then give it one more whisk.
There is no need to leave the batter to stand, so make it whenever it’s convenient.
If you are cooking your Yorkshire to accompany a roast, about 15 minutes before the joint is due to come out of the oven, increase the heat to 220°C, gas mark 7 add the dripping (or oil) to the pan and place it in the oven to heat, for 10 minutes.
While your meat is resting, or when you are ready to cook the Yorkshire, place the pan or tin over direct heat, turned to high, while you pour the batter into the sizzling hot fat.
Immediately return the tin to the highest shelf in the oven (or, if you have roast potatoes on that one, the second highest).
The pudding will take 25-30 minutes to rise and become crisp and golden.
Serve as soon as possible: if it has to wait around too long it loses its crunchiness but if it does pop it under a hot grill or back in the oven to crisp up.