On low heat, melt butter until milk solids begin to bubble and brown. Be careful not to let it burn! Turn off and set aside to cool slightly.

Add flour, baking soda, baking powder, and salt to a bowl and whisk.

In another bowl add brown and white sugars and whisk. Add chocolate chips until mixed well.

Mix the dry ingredients together.

Whisk egg, vanilla, and sourdough until well mixed.

Add egg mixture and cooled butter to dry ingredients and mix until just incorporated.

Cover dough with plastic and refrigerate for at least a few hours or up to 3-4 days for long fermentation.

When dough is ready for use, preheat oven to 375°F.

Shape cookie dough into rough balls 1 ½ - 2 inches in diameter. Place on parchment-lined baking sheets with room to spread.

Bake for 12-15 minutes until edges are just starting to lightly brown and centers might still look slightly wet.

Remove from oven and allow to cool for 5 minutes before transferring to a rack to cool completely.