Preheat oven to 425º
In a large bowl, combine flour, baking powder, baking soda, salt and sugar.
Using a pastry cutter, cut in butter into very small pieces, working it into the flour.
Mix in sourdough discard and milk and work to form a sturdy dough.
Roll out dough onto a floured surface to about 1"-1 1/2" thick. Use a cookie or biscuit cutter to make even sized biscuits.
Place on a parchment lined cookie sheet and bake for 15-18 minutes or until tops are browned and dough is cooked through.
Enjoy!