Preheat oven to 400 degrees F. Prepare a 9x13 baking dish with nonstick cooking spray. In a large mixing bowl, beat the egg.
Add the sour cream and whisk until well combined. Add the cold grated butter to the sour cream mixture and stir until combined.
To the mixing bowl, add the remaining ingredients and stir until well mixed. Turn the shaggy dough out onto a lightly floured surface.
Using well floured hands, knead the dough a few times and shape the dough into a rectangle. Roll the dough until about 1 inch thick.
Using a biscuit cutter, press straight down into the dough without twisting (to avoid sealing the dough.) Place the biscuits into the prepared baking dish.
Reshape the dough and continue cutting biscuits until all of the dough is used. Bake for 15 to 18 minutes or until the tops begin to brown and middle is cooked thru. Remove them from the oven, off baking sheet and set on a cooling rack so they don't continue baking
Prior to serving, brush the warm biscuits with melted salted butter to add moisture and more flavor.