By gum, and all that jazz.
Recording for my own reference before I forget, since they've never been quite this good before...
70g plain flour
salt & pepper
fat for cooking (I used Trex)
Beat the eggs and flour together with a whisk until smooth. Mix the milk in, in three or four goes, combining it well each time and adding seasoning on the last one, then give it a good old beat to get some air in. Leave to stand while you sort out the tin.
With the oven already cooking the beef (mine was at 170-180°C), place a dot of Trex in 8 holes of a muffin pan. (Dot = chickpea size or a bit bigger, although surely no true Yorkshireman would fart about with such airy fairy rabbit food.) Give the pan a good 15 minutes or more to heat up - I put the pan on the top and moved the meat and roasties to the bottom shelf.
20-25 minutes before you want to serve your roast dinner, quickly whip out the pan, add the batter mix to the eight holes (get the right eight!) and return to the oven. After this, open the door as little as possible - I had to open once to get the meat out to rest. Watch and wait. If they don't rise after all that, don't blame me! These ones did receive genuine Yorkshire approval.