Place the baby potatoes in a large pan of salted water and bring to the boil. Simmer on a medium heat for 20 minutes. Remove from the heat and strain then slice the potatoes into quarters and place on a baking tray.
Drizzle with some oil and season well. Place in the preheated oven for 30 minutes until golden brown.
In the meantime, heat a large pan until smoking hot. Rub the pork medallions with some oil and place on the pan. Cook, turning as necessary, on a medium heat until the juices run clear when pierced with a sharp knife.
In the meantime, heat 1 tbsp olive oil and the butter in a second pan and add the onions, wholegrain mustard and apple. Cook on a medium heat until softened and lightly coloured. Add the cider and stock to the pan. Adjust the seasoning and continue cooking until the apples mash down and the liquid has reduced by half.
Remove from the heat and using a whisk combine to create an apple mash.
Serve the medallions with the apple mash and the baked baby potato.