Method

Pop the flour into a bowl and make a well in the center
Break the egg into the well and beat and gradually incorporate the flour, then the milk, followed by water, chives, horseradish, salt and pepper
Add the dripping to the roasting tin and place in a hot (220C) oven, get sizzling hot (10 minutes)
Pour the batter into the sizzling hot fat. Return to the oven immediately
The pudding will take 15-20 for mini yorkies, 20-30 minutes for individual yorkshire puddings for Sunday roast to rise and become crisp and golden; if they are still limp, pop them back for another few minutes
To make the horseradish crème fraiche, combine the cream with freshly grated horseradish to taste
Serve as soon as possible: if it has to wait around too long it loses its crunchiness, but you can just flash it through the oven to crisp up again and freezes well.
Serve with beef and crème fraiche

If they have not risen it could be because:

• the oven was not hot enough
• the oil was not hot enough when you poured the batter in
• the oven was opened before the pudding was set