Briefly heat the potatoes from the day before in the microwave so that they can be mashed and shaped more easily. Let freshly cooked potatoes cool down briefly.
In a large bowl, mash the potatoes with the butter, milk and an egg until the consistency is even.
Pour the mixture into a piping bag (or a freezer bag with the corner cut off) and pour evenly onto a baking sheet lined with baking paper. Carefully spread a little egg yolk on each crown and finally sprinkle a little noble sweet paprika over it. Bake the potato crowns in a preheated oven at 200 ° C for about 20 minutes.