Preheat the oven to 425˚C.
Brush 6 popover cups with oil or butter or spray them. Put the tray into the oven to preheat.
Use a big bowl. Put in the flour and salt. Mix them together.
Use a big jug. Put in the milk and eggs. Whisk together. Add to the flour, whisking very well until you have a smooth, liquid batter. We recommend whisking for 3 minutes.
Gradually whisk in the melted butter until just incorporated.
Take the pan out of the oven. Immediately pour the batter into the popover pans, dividing it evenly among 6 of them.
Bake for 20-25 minutes.
Prick with a sharp knife, remove from the pans, and serve at once with butter and jam.
