Preheat the oven to 450.
In a small bowl, whisk together the flour, salt, baking soda, and baking powder.
Grate the frozen butter on a box grater. Add butter to the flour mixture, working it into butter with hands, rubbing larger pieces between fingers until flour looks like course sand. Add Pecorino and pepper and mix gently. Pour in the buttermilk. Knead dough slightly, being careful, not to overwork
Place dough onto a floured counter and knead it 2 or 3 times.
Form dough into a rectangle, 1" thick. Cut biscuits into squares.
Arrange the biscuits on a cookie sheet lined with parchment paper. Brush each biscuit with egg wash.
Bake for 9-10 minutes, or until lightly golden on top.