Preheat your oven to 220ºC/425ºF/gas 7. Lightly toast the hazelnuts in a dry frying pan, then crush with a pestle and mortar.
Whisk the egg and milk in a small bowl. Sift the flour and bicarb into a large mixing bowl, then stir in half of the toasted nuts, the chocolate chips and a pinch of sea salt. Make a well and pour in the eggy milk, then mix in enough of the buttermilk to bring it into a ball of dough.
Knead on a floured board for a few seconds, pat into a 15cm round and place on a non-stick baking tray. Cut a deep cross in the top, then scatter over the oats and remaining nuts.
Bake for 40 minutes, reducing the oven to 200ºC/400ºF/gas 6 after 15 minutes. Turn the bread over and bake for 5 more minutes, or until it sounds hollow when the base is tapped. Enjoy while still warm.