In a bowl, place the milk, lemon juice and sugar together and whisk. Leave to stand for 5 minutes. The milk will take on a curdled appearance but that's fine.
In a bowl, sift the flour and bicarbonate soda and whisk in the curdled milk mixture.
Whisk in the egg and cooled, melted butter until well combined.
Heat a non-stick pan over a medium heat and place a knob of butter into the warmed pan. Roll it around to grease the surface and cook half cup measures of the batter until bubbles appear. Flip and cook to golden and serve.