1. Preheat oven to 425º. If using a 10 inch cast iron skillet, place on stove burner and set to a low temp to begin heating the pan up. (If you are using a 9x13 inch pay, spray with non-stick spray and set aside.
2. Beat egg in a medium sized mixing bowl. Stir in buttermilk and vanilla. Add flour to buttermilk mixture about ⅓ of the total amoun at a time, stirring until combined between each addition.
3. Combine baking powder, baking soda, salt and sugar. Pour onto dough. Since 4 tablespoons butter into several small cubes. Mix with a fork until everything is incorporated.
4. Add blueberries and stir to combine. Place remaining 2 tablespoons butter in whatever pan you’re cooking the biscuits in. You want to pace biscuits in a hot pan where you’ve melted the 2 tablespoons of butter, so if you’re using cast iron, you can pe-heat the pan on the stovetop. All other pans need to be placed in the oven with the butter, then remove once butter is melted.
5. Scoop out about 3 tablespoons worth of dough. Arrange in the melted butter.
6. Bake at 425º for 15-18 minutes.
7. Serve warm, tipped with a simple glaze, if desired.
8. Simple glaze; Whisk together ½ cup powdered sugar + 2 tablespoons melted butter + 1 tablespoon milk.