If you can, prepare the batter in advance. An hour or two is perfect.
Whisk the eggs in a bowl or jug (I like using a jug because it's easier to pour the batter into the muffin tin).
Add the flour and salt, and whisk until well combined.
Add the milk, and whisk until you are left with a smooth batter (and no lumps). Leave to one side until you are ready.
Pre-heat the oven to 200°C (392°F).
Pour one teaspoon of oil (or whatever you are using) into each hole of a 12 hole muffin tin. Place the tin in the oven for 10 minutes so that the oil is nice and hot.
Take the tin out and pour in your batter until the muffin holes are about half full (be careful not to overfill).
Bake for around 12-15 minutes (do not open the oven or the puddings will instantly deflate).
Eat immediately with your favourite roast or dish!