oven may not be hot enough, ditto fat. My failsafe recipe. plonk an egg in the bowl and sprinkle in flour (plain) whisking together until you have a really thick batter, only just runny, more blobby than liquid. thin to the consistency of thick custard. Add a pinch of salt if you like. Stick in a cool place for a while, covered. When you are ready to cook, have the oven hot and the oil or fat almost smoking hot...give the batter a good stir then get the fat out of the oven. When you get it out of the oven there should be a distinct heat shimmer. Pour in the batter, there should be a sizzle and the batter should start to cook around the edge. Put the tin back in the hot oven and don't open the door for around 10 minutes.