Make sure your butter is very cold. You can pop in the freezer for a few minutes.
Preheat your oven to 425℉
Using your large bowl, combine the flour, salt, baking powder and sugar together and give a good stir to incorporate everything well.
Take the food grater and grate the butter over the bowl and into the flour.
When you finished grating the butter use the pastry cutter to cut the butter into the flour. You can also use a fork for this part. Your flour will turn crumbly.
Pour milk and the sourdough discard into the center of the bowl and using a fork mix in the flour gently until it is well incorporated. If your dough is very dry and you have a lot of flour add in a tablespoon of milk or two until it isn't as dry.
Turn the dough onto a lightly floured counter and roll flat. About 1/2 inch thick or thinner depending on your preference.
Use the biscuit cutter to cut as many biscuits as you are able with the amount of dough you have. Keep folding the dough, rolling it flat and cutting biscuits until you are out of dough.
Place biscuits on an oiled baking stone.
Bake at 425℉ for 14-16 minutes or until golden on top.
Serve with butter and favorite jam and enjoy!