Use one cube or 113 grams of salted butter to create the 90g of browned butter. Slowly melt and simmer the butter, in a small skillet or sauce pot, until it turns into a caramelized brown color. Watch closely and remove from heat quickly as it's easy to burn. Once the butter has simmered long enough to brown it should be reduced to approximately 90grams total of melted and browned butter.
Mix together the granulated sugar, brown sugar and melted butter.
Add the sourdoughs starter and vanilla and beat well by hand until smooth and well combined. Let cool before adding the chocolate chips.
Sift or stir together the flour, baking soda, baking powder and salt and mix in thoroughly.
Mix in the 110 grams of dark chocolate chips. Chill the dough at least one hour. If I do the minimum time of one hour, I spread the dough up onto the sides of the bowl so it's thin and chills quicker. Or let the dough sit in the fridge until you are ready to bake at another time.
Pre-heat your oven to 375 degrees. Divide the dough into 50gram portions and roll into large balls and place on a parchment paper lined baking sheet at least 2 inches apart.. Bake in the pre-heated oven for approximately 11-13 minute or until golden brown around the edges and not quite set in the middle.
Remove from the oven. Use extra chocolate chips to fill in any empty looking areas on the cookies. Using a spoon or your fingers (carefully, they are hot!) nudge in the edges of the cookies. Remove from the baking sheet and allow to cool completely.
Store in an airtight container.
Serving Size 1 cookie