Preheat oven to 180°C. Grease a 20cm (8-inch) square cake pan; line base and sides with baking paper, extending paper 5cm (2 inches) over sides.
Beat eggs in a medium bowl with an electric mixer on high speed for 10 minutes or until stiff peaks form.
Meanwhile, place chocolate-hazelnut spread in a large microwave-safe bowl; microwave on HIGH (100%) for 20 seconds or until softened slightly.
Fold egg mixture into chocolate-hazelnut mixture, in three batches. Pour mixture into pan; bake 15 minutes. Remove from oven; sprinkle with combined choc bits. Bake a further 10 minutes or until a skewer inserted into centre comes out clean. Cool in pan before cutting.
Brownies will keep at room temperature, in an airtight container, for up to 3 days.