Bring a large saucepan of water to the boil over a high heat. Add the potato, apple and garlic and cook until tender, about 10 to 12 minutes. Drain well and allow to air dry for a few moments.
Wipe out the pan the potatoes were cooked in and heat gently, add the butter and melt, then add the potatoes and apples and mash well with the cream or milk; season with salt if using, and pepper and mix until smooth. Stir in the mustard and nutmeg, if using.
Serve piping hot in scoops, make a little well in the centre and add a little more butter whilst still hot if liked.
Email me with queries at email@example.com as I made this up!