Sift the plain flour (100g) and salt (about 1/4 tsp) into a large bowl.
In a separate bowl, beat the egg (1 egg) and then add it to the flour.
Add about a quarter of the milk (75ml) and whisk until combined.
Gradually add the remaining milk (225ml) whisking to combine each addition before adding more - Using this method should mean that you don't get lumps. However if you find a few have crept in then either pass your batter through a sieve, or blitz it briefly with a hand blender.
Melt the butter (25g) in a frying pan on a low heat (so that it doesn't burn) and then tip it out of the pan into a cup or bowl.
Turn up the heat to medium and then once the pan is hot, add about two tablespoons of batter (assuming 6" pancake), immediately swirl the batter around the pan so that the base is coated. If there's any excess batter, tip it back into the bowl -
if you have too much batter in the pan you'll end up with thick, stodgy pancakes.
Cook for about 1 minute until brown and then flip and cook on the other side for a further 30 seconds.
Dip some kitchen paper into the melted butter and spread it around the pan, and the repeat the process (from step 6) until all of the pancakes are cooked.