Preheat oven to 35o degrees

Add onion to buttermilk to soak and set aside

Mix the flour, baking powder, sugar and salt in a bowl and set aside

Cut diced cold butter into dry ingredients until small pebbles form

Break egg up in buttermilk and onion mixture

Pour wet ingredients in with the dry and stir until just combined

Drop by spoonful onto a baking sheet lined with parchment

Bake for 15 minutes

Brush the top with melted butter

Place back in the oven for another 5 min until the biscuits are golden brown