Brush the trays with some vegetable oil, and place in the oven to heat the oil- for perfect puddings, the oil needs to be piping hot.
Add the flour, eggs, milk and salt to a bowl. Mix with an electric mixer until smooth.
For ease, transfer the mixture to a jug, and pour the mixture into the heated trays, leaving little bit of space in each circle between the top of the mixture and the tray surface.
Cook for 20-25 minutes at the top of the oven, when they should be evenly golden brown, a little bit darker at the top. Do not open the door while cooking, as this will make the puddings sink and not cook properly.
Notes
For best results, use a Yorkshire pudding tray, but if you don't have one, use a shallow cupcake tray (puddings will likely stick in deeper trays)