Preheat oven to 350 degrees F
Mix flour, baking soda, baking powder and salt in one bowl.
Using your mixer cream together the butter and sugar.
Add eggs to the butter mixture one at a time making sure each is mixed in before adding the next.
Add the vanilla extract and orange zest to the egg and butter mixture.
Add the flour mixture to the eggs and butter and mix until combined.
Slowly pour in the buttermilk until it is fully incorporated.
Fold in the cranberries and chopped walnuts.
Grease your 9x5 inch loaf pan and either flour the bottom or line it with parchment paper.
Pour the batter into the loaf pan.
Bake for 55 minutes or until a toothpick inserted in the center comes out clean. Make sure to check it early and often so it doesn't over-bake.
Once it has finished baking remove it from the oven and let it cool in the pan for 15 minutes before removing it from the pan and letting it cool completely.
Once the bread has cooled melt the while chocolate melts in the microwave for 30 seconds at a time until they are fully melted and smooth. Then drizzle over the top of the bread.
Let the chocolate cool and firm up and then slice and serve.