In a bowl of a food processor, combine cheese, semolina, egg yolk, sugar, and salt. Process until mixed well. Transfer into a container with a lid. Refrigerate for at least 2 hours (or better overnight) to properly hydrate semolina.
Meanwhile, prepare the crunchy topping. In a frying pan, melt butter, add breadcrumbs and nuts and fry until golden, stirring. Add turbinado sugar and stir to let it melt, mix with butter and turn into caramel, coating breadcrumbs. You can make it in advance and keep in an airtight closed container until ready.
Start boiling water in a pot. The diameter of the pot should be large enough to fit all dumplings you are making in a single layer. The water should be 4-5" deep.
Moisten your working surface, the measuring scoop (2 oz), and your hands. Follow the instructional video to stuff and shape dumplings.
Carefully place shaped dumplings into slowly boiling water. They will sink to the bottom first. Give them a few minutes to start floating and let them cook for about 2-3 more minutes. Meanwhile, spread some sour cream on the bottom of your serving bowls and keep them ready.
Strain cooked dumplings, 2-3 per portion. To serve, drizzle them with maple syrup. and sprinkle with the crunchy topping. Smachnogo!