Begin by preparing the mashed potatoes. Peel and boil the potatoes until tender, then mash them until smooth. Allow them to cool slightly.
In a large mixing bowl, combine the mashed potatoes, flour, baking powder, and salt. Mix until well combined.
Add the softened butter and milk to the mixture. Stir until a dough forms. If the dough is too sticky, add a little more flour; if it’s too dry, add more milk, one tablespoon at a time.
Turn the dough out onto a floured surface and knead gently for about 1-2 minutes until smooth.
Divide the dough into two equal portions and shape each into a round disc about 1/2 inch thick.
Heat a non-stick skillet or griddle over medium heat. Cook each disc for about 5-7 minutes on each side, or until golden brown and cooked through.
Remove from the skillet and let cool slightly before slicing.