Preheat your oven to 350 degrees Fahrenheit. Melt your butter, then set it aside to cool until warm. Prepare your loaf pan by greasing it with butter or lining it with a piece of parchment paper.
Add the cooled butter, white and brown sugar, vanilla, eggs, sourdough discard or active starter, and milk to a large mixing bowl and whisk together until smooth.
In a separate small bowl, combine the flour, salt, baking powder, and baking soda. Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Gently fold in the chocolate chips with a spatula, then transfer the batter into the prepared loaf pan.
Bake in the preheated oven for 65-75 minutes until golden brown, and a toothpick comes out clean.
Cool before slicing.
Notes
Avoid over-mixing the batter.
When baked, the top should be golden brown and set. A sharp knife, toothpick, or cake tester inserted in the center should come out clean.
Cooling in the pan completely will help the bread to slice cleanly.
Find the long fermentation instructions in the blog post.