Preheat your oven to 180°C. Once hot, pour your oil into your skillet or baking dish, then add it to the oven whilst you make your Yorkshire pudding batter.
For the Yorkshire pudding, mix your flours, egg and milk together in a bowl, whisking until you have a smooth batter which resembles double cream.
Remove your skillet from the oven, then pour the batter over the hot oil, then bake for 20-25 minutes until golden brown.
Prep the rest of your fillings whilst your Yorkshire pudding is baking, then once risen and golden brown, remove from the oven, blotting any excess oil out of the centre, then fill your Yorkshire pudding and pour over your gravy.