In a small bowl, mix the sugar, flour, and cinnamon until well combined. Add the butter and stir until it clumps together. Chill while you make the batter.

Preheat oven to 350 degrees Fahrenheit (177 Celsius). Butter an 8x5-inch loaf pan and line it with parchment paper.

In a medium bowl, whisk together the sourdough starter, butter, oil, brown sugar, maple syrup, eggs, pumpkin puree, and vanilla extract until well combined.

In a separate, large bowl whisk together the flour, salt, baking soda, baking powder, and pumpkin spice. Add the wet ingredients to the dry ingredients and fold together just until combined. Don't over-mix!

Scrape the batter into the prepared pan. Smooth out the top and sprinkle the streusel on top if using. Bake in the preheated oven for 55-65 minutes, or until a toothpick inserted near the center comes out clean. If the streusel starts to brown too much before the loaf is done baking, you can put a tent of aluminum foil on top.

When the loaf is done baking, allow to cool in the pan on a wire cooling rack for 10 minutes before removing from the pan. Allow to cool completely on the wire rack before slicing.

In a medium bowl, beat the cream cheese until smooth. Add the maple syrup and beat again until smooth. Sift the powdered sugar over the mixutre and add the vanilla extract. Beat until completely smooth.

You can add a bit of cream or milk to thin out the batter if needed. You want it to be thin enough to drizzle, but thick enough that it won't run right off of the loaf.

Drizzle all over the loaf. If you have extra frosting, you can spread it on individual slices of bread!

If you opt to leave off the frosting, you can store the bread in an airtight container at room temperature for up to 1 day. After that, it's best store it in the refrigerator.

If you drizzle the frosting on top of the bread, you'll want to go ahead and store it in the refrigerator right away. It should keep for up to 5 days if you wrap it well.

Quick tip: Place the piece of parchment paper that you used to line the pan on top of the frosting to prevent it from transferring to the storage container. You could also use a bit of plastic wrap.