Peel and cube potatoes into bite-sized chunks
Cut cooking apples into similar-sized chunks as the potatoes
Combine equal parts potatoes and apples in cold water
Boil potatoes and apples until soft
Melt butter in a separate pot and add sliced onions
Caramelize onions by covering and stirring every 3-4 minutes, scraping the bottom
Uncover onions, add salt, and finish cooking uncovered until caramelized
Strain the cooked potatoes and apples and let them steam dry for about 5 minutes
Transfer to a pot with thinly sliced butter
Mash with a potato masher to a chunky consistency
Season with salt, white pepper, and freshly grated nutmeg
Mix well and transfer to a serving dish
Make a well on top and fill with caramelized onions
Drizzle melted butter over the top and serve
