Let the butter melt in a saucepan. Once melted, let it cook further for around 3-4 minutes, stirring occasionally until the milk solids have caramelized and the butter smells nutty. 130 g butter
Pour the browned butter and all the browned bits into a large heat-proof bowl. Allow it to cool at room temperature for about 15 minutes.
Add the sugar, sourdough starter, vanilla, and egg to the cooled butter, and beat it until well combined. 100 g soft brown sugar, 100 g granulated sugar, 100 g discard sourdough starter, 1 large egg, 1 teaspoon vanilla extract
Mix the flour, baking soda, and salt in a separate bowl. 190 g all-purpose flour, 3/4 teaspoon baking soda, ½ teaspoon salt
Stir the flour mixture into the cookie dough mixture until a dough forms, then add the chocolate chips. Continue stirring until it's all combined. 170 g chocolate chips
Cover the bowl and place the dough in the refrigerator for at least 2 hours or overnight.
Preheat the oven to 350°F/180°C and line cookie sheets with parchment paper.
Roll the cookie dough into balls using a medium cookie scoop or around 1 1/2 tablespoons of dough. Space them at least 2 inches apart on the cookie sheets. Press a few extra pieces of chocolate into the tops of each ball.
Bake the cookies for 10–12 minutes, until they have puffed and the edges are golden brown.
Tip: To make your cookies perfectly round, use a round cookie cutter slightly larger than the cookie and gently swirl it around each one right after baking. This neatens the edges while the cookies are still soft and warm.
Let them cool to room temperature on a wire rack.