Preheat the oven to 350°F (180°C) and butter and flour a 9-inch by 5-inch (23cm x 13cm) loaf pan.

In a bowl, mix flour, cinnamon, baking powder, baking soda, salt, ginger, and allspice together until well combined.

In another bowl, combine the pumpkin puree, 1 cup (6oz/170g) brown sugar, buttermilk, eggs, oil, and vanilla extract.

Pour the wet ingredients into the dry ingredients and mix until just combined.

Remove 1 cup (8oz/225g) of the batter and place it in the bowl that held the wet ingredients.

In a microwave-safe bowl or in a small pan over a low flame, combine chocolate and cream and heat until melted.

Add the chocolate mixture and the remaining ¼ cup (1 1/2oz/43g) of brown sugar to the cup of batter and gently whisk to combine.

Spread 1/3 of the pumpkin batter in the bottom of the loaf pan. Top with ½ of the chocolate batter. Top the chocolate batter with another 1/3 of the pumpkin batter, then add the remaining chocolate batter. Finish with the final third of the pumpkin batter.

Run a thin knife through the batter in an “s” pattern just once or twice (take care not to mix too much – you want to keep the colors swirled but separate).

Sprinkle with the granulated sugar (if using) and bake for roughly 50 minutes, or until a toothpick comes out clean.

Let cool for 15 minutes before inverting onto a wire rack to finish cooling.

Store in an airtight container at room temperature or in the refrigerator for up to three days. You can also freeze this bread in an airtight container for up to 2 months.