Preheat the oven to 200°C/180°C fan/gas mark 6 and line a 1lb loaf tin with baking parchment. Unroll the dough and spread 60g chocolate spread across the top. Roll the dough up along the longest edge to make a tight roll, leaving the seam face down on the surface.
Cut the dough in half down the entire length, then wrap each piece around each other to make a two-piece braid. Layer the braid into the prepared loaf tin, folding it back and forth to fit the length of the tin. Brush the top with the beaten egg, then bake for 45 minutes, loosely covering with foil for the last 15 minutes. The loaf should sound hollow when tapped on the bottom when it’s ready. Turn the loaf out carefully onto a cooling rack and allow to cool completely.
Toast the hazelnuts in a dry frying pan for 2-3 minutes until they smell fragrant, then roughly chop. Put the remaining chocolate spread into a small saucepan set over a low heat and warm to make it slightly runny. Drizzle the chocolate spread over the loaf and scatter with the hazelnuts.