Preheat oven to 400 °F. Prepare a baking sheet with a piece of parchment paper.
In a large bowl, combine flour, sugar, baking powder, baking soda and salt.
Cube your cold butter and add to flour mixture. Combine with a pastry blender until butter pieces are pea size, resemble coarse crumbs, and are evenly distributed throughout dough.
In a separate bowl, whisk egg until lightly beaten. Then add the sourdough discard and milk to the egg. Whisk until combined.
Make a well in the dry ingredients and add the egg /sourdough discard wet ingredients to create the scone dough.
Mix using a rubber spatula until the flour is hydrated and the dough just comes together. Don't overwork. The dough will look shaggy.
Add white chocolate chips and evenly distribute throughout the dough.
Form the dough into a ball on a lightly floured surface and then divide dough into half using a bench knife.
Place one portion of the dough on a lightly greased parchment paper on a baking sheet. Press into a 6-inch round disc, about ¾ to 1 inch thick. Cut the disc into 6 equal wedges.
Repeat this process and cut scones from the other dough portion.
Bake for 15 minutes until golden brown. Cool on baking tray for 5 minutes before serving.