Heat oven to 220C/200C fan/gas 7. Put 1 tsp oil in each well of a 12-hole muffin tin and heat in the oven for 6 mins. Meanwhile, tip the flour and some seasoning into a large, wide jug or a bowl. Beat the eggs with the milk and mustard, then gradually beat into the flour mixture until it makes a smooth batter.
Pour or ladle the batter into the tin, taking care that it doesn’t splatter up and burn you. Bake for 25-30 mins until well risen and golden – try to keep the door closed, as this will help you get a good rise on the Yorkies.