1. 1. Combine Starter and Wet Ingredients: In a large mixing bowl, gently whisk together the active sourdough starter, warm milk, granulated sugar, salt, and the large egg until well combined. The mixture should look slightly frothy and uniform.

2. 2. Add Flour and Butter to Form the Dough: Gradually add the all-purpose flour to the wet ingredients, mixing with a wooden spoon or your hands until a shaggy dough forms. Turn the dough out onto a lightly floured surface and knead for about 5 minutes. Incorporate the softened unsalted butter, kneading until the butter is fully absorbed and the dough is smooth and elastic, about another 5-7 minutes. Place the dough back into a lightly oiled bowl, cover, and let it bulk ferment in a warm spot for 4-6 hours, or until it has visibly increased in size and is bubbly. Alternatively, you can refrigerate it overnight for 8-12 hours for a slower fermentation.

3. 3. Prepare Pumpkin and Chocolate Swirls: While the dough is fermenting, or once it’s ready, prepare your two separate fillings. In one small bowl, mix the pumpkin puree with the pumpkin pie spice until well combined. In another small bowl, melt the chocolate chips in the microwave in 30-second intervals, stirring until smooth.

4. 4. Shape the Dough and Spread Fillings: Once your dough has completed its first rise, gently punch it down and turn it out onto a lightly floured surface. Roll the dough into a large rectangle, approximately 12×18 inches. Spread the spiced pumpkin puree evenly over one half of the dough rectangle, leaving a small border. On the other half, spread the melted chocolate evenly, also leaving a small border.

5. 5. Create the Swirl: Fold the pumpkin-covered side of the dough over the chocolate-covered side, creating a layered rectangle. Gently press down to seal. Now, roll this layered dough tightly from one of the long ends to form a log. Pinch the seam closed.

6. 6. Second Rise and Prepare for Baking: Carefully transfer the dough log to a lightly greased 9×5-inch loaf pan. Cover the loaf pan loosely with plastic wrap or a clean kitchen towel and let it rise in a warm place for 1-2 hours, or until it has nearly doubled in size and looks puffy. Towards the end of the second rise, preheat your oven to 375 F (190 C).

7. 7. Bake the Bread: Once the oven is preheated, brush the top of the risen loaf with the melted butter. Bake for 35-45 minutes, or until the crust is golden brown and the internal temperature reaches 200-210 F (93-99 C) when checked with an instant-read thermometer. If the top starts to brown too quickly, you can loosely tent it with aluminum foil.

8. 8. Cool Before Slicing: Remove the loaf from the oven and let it cool in the pan for 10-15 minutes before carefully transferring it to a wire rack to cool completely. Slicing too early can result in a gummy texture. Allow it to cool for at least an hour before enjoying.