Preheat oven to 425 F. In a measuring cup, whisk together milk and vinegar. Let sit for 5 minutes.
In a large bowl, whisk together flour, salt, baking powder and baking soda. Cut butter into the mixture using either a pastry blender or two knives until mixture resembles course crumbs.
Pour in milk and mix with a fork until a wet dough forms. Dump dough out onto a floured surface. Fold dough over itself a couple of times. Gently pat out dough into a rectangle and cut out biscuits with a floured cutter.
Place biscuits onto a large greased baking sheet. Brush with melted butter. Bake for 12-15 minutes.
