Melt the butter in a pan, on a very very low heat!
Pour the butter into a mixing bowl with caster & light brown sugar and mix with a wooden spoon/spatula until fully combined. Should take about a minute.
Crack the egg into the same bowl. Mix together until just combined. Set aside.
Put the flour, salt and baking powder into another bowl. Stir with a spoon so that its all evenly mixed together.
Add the flour to butter/sugar mixture & stir until fully combined. Note – It will look like a lot of flour! Keep stirring and it’ll all come together. Promise!
Cover with cling film and place into the fridge for at least an hour.
Remove from the fridge and divide into 14 balls – about golf ball sized.>The mixture should not be too sticky at this stage. If it is, place it back in the fridge to firm up.
Place onto baking parchment on a baking tray, leaving lots of room around them. Put into the oven for 12-15mins at 175oC until the edges are browning but the middles are still gooey.
Remove from the oven and carefully cut them down the middle - just off centre like my picture. Leave to cool on the baking tray for at least 10-15mins before attempting to move them – they are VERY fragile when warm but they harden up once they start to cool.