Melt the fat in a small pot, let it cool down a little. Put 1/2 teaspoon of oil in each of 12 hollows of a popo tray. Place the tray in the preheated oven (electric cooker: 225 °C/ circulating air: 200 °C/ gas: see manufacturer)
Beat the eggs, milk, fat and 1/2 teaspoon salt briefly with a whisk. Add the flour at once and mix until the dough just has no more lumps. Do not stir too long! Pour the dough into a measuring cup
Remove the tray from the oven. Pour the dough into the prepared trays. Bake in the hot oven for about 15 minutes. Reduce temperature (electric oven: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) and bake for another 10-12 minutes. Do not open the oven door during the entire baking time. Serve popovers warm