A proper Yorkshire Pudding (note not plural) is as follows:
serves approx 10 people, depending on how big the slices are:
mug of plain flour
mug of milk
2 or 3 eggs
lots of salt and pepper
whisk all that together. There is no need to let it stand.
Put your oven on the highest it will go. Get a roasting dish and put a 'healthy' (!) piece of lard (not oil, lard) in it - enough so when it is melted it covers the whole dish. Wait till the lard is smoking, then pour the batter in. try to do this quickly so the oven and lard do not lose any heat.
Close oven door. Don't open it too much (if at all) while cooking. Should take about half-an-hour. Cut it up and serve.
Same sort of thing for the cupcake versions. Lard in each one, wait till it smokes, pour batter in quickly. Shove in oven.
Cue mass debate...!
If I was you, I would do a few practice runs.