1. Preheat the oven to 170°C; spray a 9-by-13-inch pan with nonstick cooking spray.
2. Stir together the chocolate-hazelnut spread, flour and eggs in a medium bowl. Pour into the prepared pan and spread the mixture to the edges.
3. Bake until the surface looks set and slightly crisp, about 25 minutes. Let cool slightly, then cut into squares and enjoy!