How to Make It
Put the potatoes and cabbage in a large saucepan, cover with water and bring to a boil. Add salt and simmer over moderately high heat until the potatoes are tender, about 20 minutes. Drain in a colander and return to the pan. Shake the pan over moderately high heat to dry out the potatoes. Remove from the heat. Using a potato masher, mash the potatoes with the cabbage. Mash in the butter and olive oil. Stir in the milk, season with salt and pepper, then serve.