Whisk together flour, granulated sugar, baking powder, baking soda, and salt in a medium mixing bowl. Set aside.
Grate frozen butter using a cheese grater or cube butter into small pieces. Add to bowl with dry ingredients. Place in refrigerator for at least 30 minutes.
While your flour mixture is chilling, line a cookie sheet with parchment paper. (See recipe note if you do not have buttermilk. This is a good time to prep your makeshift buttermilk!)
Take the bowl out of the fridge and use a pastry cutter to work together the butter with the flour. The butter pieces should become pea-sized and evenly coated with flour. Use a spoon to make a well in the middle of the bowl.
In a separate small bowl, combine the buttermilk and vanilla. Add this mixture to the middle of the well in your other bowl. Use a wooden spoon to stir the mixture. It should become shaggy and can keep its shape if pressed together. Gently fold in the frozen berries, being careful to not crush them.
Take a 3" round cookie cutter and place it on your cookie sheet. It works best if you line up your rows of scones as you are shaping them. Start in the top left corner and work your way down, making sure to leave enough space in between scones for them to spread in the oven. They will spread quite a bit even after freezing! I recommend about 9 scones per cookie sheet.
Stuff your shaggy dough into the cookie cutter, pressing down to make it compact. This is what makes the dough stick together. Keep pressing down and filling with more dough until you reach the top of the cookie cutter. Lift the cookie cutter off the dough (you can press the dough through the cookie cutter gently and wiggle the cutter away). Repeat with the remaining dough. Sprinkle scones with course sugar.
Cover scones with plastic wrap and place them in the freezer for about 20-30 minutes. This helps the butter harden again which will make it spread less in the oven.
Preheat oven to 375 degrees. Bake scones for 15-20 minutes. Transfer scones to a wire rack to cool for about 10 minutes before serving.
(Optional) If you want to use a glaze, whisk together powdered sugar, cream, and vanilla until smooth. Drizzle over scones after they have cooled for 10 minutes. Enjoy!