Position racks in the center and top third of the oven and heat to 375°F. Line two large baking sheets with parchment paper.
Process the hazelnuts, sugar, and cinnamon in a food processor fitted with the metal blade until the nuts are very finely chopped. Transfer to a bowl.
Cut the dough into two pieces. On a lightly floured work surface, roll out half of the dough into a 12 X 8-inch rectangle. Brush the dough with half of the melted butter. Sprinkle with half of the hazelnut sugar, then sprinkle with ¼cup of the currants. Starting at a short end, roll up the dough into a tight cylinder, pinching the long seam closed as best as possible. Using a sharp knife, without compressing the layers, cut the dough into eight 1-inch-wide slices. Place the slices 1½ inches apart on the sheets. Repeat with the remaining dough, butter, hazelnut sugar, and currants. Cover with plastic wrap and let stand until the snails look puffy, about 30 minutes.
Bake, switching the positions of the sheets from top to bottom and front to back halfway through baking, until the snails are golden brown, about 20 minutes. Transfer to wire racks and cool.
Brush the warm glaze over the snails and cool until the glaze sets.