Heat the oven to 425ºF, then put the pan in to heat while you prepare the batter. A 10- or 12-inch oven-proof skillet is ideal, but you could use a comparably-sized baking dish (Pyrex, say).

Now use a whisk to beat the eggs in a medium-sized bowl, then beat in the milk, then the flour and salt. We tend to beat the mixture until it's just smooth.

By now your pan should be very hot. Add the butter, then remove the pan from the oven and swirl it so that the butter is melted and sizzling wildly. You need to do all this quite quickly because you don't want the oven to lose its heat, you don't want the pan to cool off, and you don't want the butter to burn.

Now pour the batter into the buttery pan and return it the oven. Set your timer for 15 minutes. We bake it for 20, but I think it's worth peeking at it at 15 because your oven might be different from ours: you want it to be puffed and golden and quite brown in places.