Sift together the flour and baking powder into the bowl of an electric mixer, or a large bowl if mixing by hand
Add in the melted butter, mashed potato and buttermilk and mix well until combined and a soft dough has formed and the dough clears the sides of the bowl. Add more flour if needed (but it should be a little bit sticky)
Pop the dough onto a floured surface and shape into a rough square, about 1cm tall. Cut 9 squares out of the dough and place on a baking sheet lined with parchment paper
Bake for 18 minutes, until golden brown on top
Serve straight from the oven with lashings of fresh butter and some honey. Or wait until morning, toast up and serve with some jam/jelly
The potatoes should be warm when using them. If you are using fresh cooked mashed potatoes then thats fine, but if you are pulling leftovers from the fridge, you will need to warm them up before adding them to the recipe.