Prep. Preheat oven to 350° F. Butter the bottom and sides of a 9x5-inch loaf pan. For easy removal, line bottom with parchment paper, leaving a few inches hanging over two sides to use as handles after baking.
Brown the butter. Melt 3 oz (6 tbsp) butter. Continue to cook for a few minutes, until it takes on a golden color and starts to smell toasty. Remove from heat and allow to cool for a few minutes.
Combine dry ingredients. In a large bowl, whisk together 1 ½ cups flour, 1 tsp baking soda, 1 tsp baking powder, ½ tsp salt, 1 tsp cinnamon, and ½ tsp each nutmeg and ginger.
Combine wet ingredients. In a separate bowl, whisk together brown butter and ¾ cup brown sugar until well combined. Add 1 ¾ cups (or 1 can) pumpkin puree, ½ cup sourdough discard, 2 eggs and 1 tsp vanilla. Whisk thoroughly.
Mix batter. Combine wet and dry ingredients, folding gently with a spatula until just combined and no streaks of flour remain. Fold in chocolate chips, if using.
Bake. Pour batter into prepared pan and bake until cooked through*, about 50-60 minutes. Allow pumpkin bread to cool to room temperature before slicing.