Line a baking sheet with plastic wrap. Place 1 wonton wrapper on the work surface. Brush the edges of the wrapper lightly with egg. Spoon 1 tablespoon of chocolate-hazelnut spread into the center of the wrapper. Fold the wrapper diagonally in half over the filling and press the edges of the wrapper to seal. Place the ravioli on the prepared baking sheet. Repeat with the remaining wonton wrappers, egg, and chocolate-hazelnut spread.
Preheat the oven to 200 degrees F. Add enough oil to a heavy large frying pan to reach a depth of 2 inches. Heat the oil over medium heat to 350 degrees F.
Working in batches, carefully add the ravioli to the hot oil and cook until they are golden brown, about 45 seconds per side. Using a slotted spoon, transfer the ravioli to a plate lined with paper towels to drain. Then, transfer the cooked ravioli to another baking sheet and keep them warm in the oven while frying the remaining ravioli. (The fried ravioli can be prepared 1 day ahead. Cool them completely, then cover and refrigerate. Before serving, place them on a baking sheet and rewarm in a preheated 375 degrees F oven just until they are heated through, about 7 minutes.)
Spray the top side of the mint leaves very lightly with nonstick spray. Working with 1 leaf at a time, dredge the coated side of the leaves in sugar to coat lightly.
Arrange 2 fried ravioli on each plate. Dust the ravioli with powdered sugar. Garnish with the sugared mint leaves and serve.