Preheat the oven to 400°.

Add the sourdough starter, self-rising flour, and milk to a glass mixing bowl.

Use your kitchen grater to grate the butter into the same mixing bowl. Don't skip this step--this gives the biscuits the light, airy, texture, and buttery flavor. As you bake the biscuits, the butter dissolves, leaving heavenly little air pockets.

Use a wooden spoon to combine all the ingredients, until everything is moistened. Do not overwork the dough, as you do not want to melt the butter.

Using a spoon to scoop and lightly shape the biscuits, drop them onto an ungreased baking sheet (I used a stoneware cookie sheet).

Bake the biscuits for 20 minutes. The bottom of the biscuits will have a lightly browned bottom. Use tongs to gently flip the biscuits and bake them top down (to brown the tops) for 10 minutes.

Remove the biscuits and serve them while hot--they are best served fresh. If you don't use them right away, plan to reheat them before you eat them.