Preheat oven to 360℉. In a large mixing bowl, combine together your dry ingredients of 2½ cups flour, 1 tbsp baking powder ½ tsp salt, 1 tsp cinnamon and ¼ cup brown sugar.
With a cheese grater, grate your 12 tbsp cold butter (1½ sticks) and mix into dry ingredients with your hands or mixing spoon until it reaches a mealy texture.
In a separate bowl, whisk together 1 egg, 1 cup buttermilk, ¾ cup pumpkin purée and 1 tsp vanilla. Add to the bowl of dry ingredients and mix until just combined. This will be close to a wet dough that is sticky. Use your mixing spoon to transfer it to a parchment lined baking sheet, spread into a circle and cut into 8 slices, the same way you would a pizza.
Bake for 22-27 minutes or until lightly golden on edges and the middle is set, not jiggly. Drizzle with additional melted chocolate if desired before baking.