Lay the potatoes on a baking sheet and cook until tender when pierced with a fork, about 40 minutes. Meanwhile, while the potatoes are cooking, bring the butter and cream to a boil in a medium pot. Reduce the heat to low and keep at a simmer until the potatoes come out of the oven.
Just before the potatoes are finished cooking, soak the gelatin sheets in cold water for 5 minutes. Ring out the sheets and add them to the warm cream mixture. Whisk into the cream until the sheets dissolve.
Remove the potatoes from the oven and fill a blender with half of the cream and half of the potatoes. Using a plunger, blend until smooth. (The starchiness of the potatoes is a job for your blender, patience will be useful here.)
Transfer the blended potatoes to a bowl and repeat with the remaining cream and potatoes. Mix together the salt and sugar and taste before adding it all; depending on the person you may find it too much or not enough.
Transfer the potatoes to a parchment-lined baking sheet and let cool overnight in the refrigerator.
When ready to cook, flip the potatoes onto a cutting board and peel off the parchment paper. Cut to desired shape and size.
Preheat a deep-fryer to 350 degrees F.
In three separate shallow bowls or containers, set up your breading station. Fill the first bowl with the flour, the second with the egg and milk (whisked to combine) and the third with the panko.
Bread the potato mash pieces by first going in flour, then the egg, then the panko, then back in the egg and then the panko.
After the mash bites are breaded, you can store them in the refrigerator until ready to fry, or freeze them for long term storage.
Deep-fry the mash bites until golden brown, about 1 minute. They should be soft to the touch and warm all the way through.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.