In a mixing bowl add the flour and eggs then whisk until mixture is completely smooth. Slowly pour in the milk whilst still mixing and do the same with the melted butter. Pour some of the mixture into a non-stick pan (I’ve found that if I add oil or butter the crepe doesn’t set very well the first time). When you see bubbles of air under the surface check the underside and if cooked, flip. Flip again when the other side is cooked and serve with any filling you want!