Boil the potatoes in salted water until completely tender, about 18 minutes. Drain and pass through a ricer or potato masher. Spread on a tray to cool slightly and let some of the steam escape, about 10 minutes.

In a bowl, combine the warm potato, flour, egg, softened butter, and salt. Mix gently with your hands until just combined; do not overwork. The dough should be soft and slightly sticky.

With wet hands, take a heaping tablespoon of dough, flatten it in your palm, place a cherry in the center, and wrap the dough around it, sealing completely. Roll gently into a ball. Repeat to make 18 dumplings.

Bring a wide pot of lightly salted water to a gentle simmer. Poach the dumplings in batches for 12-15 minutes, until they float and feel firm. Lift out with a slotted spoon.

While the dumplings poach, toast the breadcrumbs in a dry skillet over medium heat, stirring, until golden and crisp, about 4 minutes. Add the butter and cinnamon and cook until the butter is deeply browned and smells like toffee, about 2 minutes more. Stir in the sugar.

Spoon the cinnamon breadcrumbs over the warm dumplings, drizzle with any remaining browned butter, and finish with a dollop of crème fraîche and a dusting of powdered sugar. Serve at once.