Bring a large pan of salted water to the boil. Add the potatoes and cook for 4 mins. Drain and leave to steam dry in a colander.

Heat half the butter and 1 tbsp olive oil in a large frying pan or shallow casserole dish over a medium-high heat. Add the apple wedges and fry on each side for 5 mins or until golden brown and starting to caramelise. Remove with a slotted spoon and set aside on a plate.

In the same pan, heat the remaining butter and a little more oil over a medium heat and add the potatoes and sausage chunks. Fry for 10-15 mins, turning every so often until the potatoes and sausage are crisp and golden brown. Season to taste. Stir through the mustard and the apple wedges, then scatter over some thyme leaves, and serve with watercress salad.