Preheat oven to 425 degrees F. Line a baking sheet with parchment paper.
In a large bowl, whisk together the flour, sugar, baking powder and salt.
Use a box grater to grate the COLD butter after it has been in the freezer for 30 minutes. Add the grated butter to the bowl with the flour mixture and toss gently with your hands.
Combine the 3/4 cup heavy cream, 3/4 cup whole milk, and vanilla in a liquid measuring cup. Pour into the dry ingredients and use a fork or your hands to mix gently until the dough starts to come together. Try not to over-work the dough.
Transfer the dough to a floured work surface. Press the dough into a rectangle that is about 3/4-inch thick. Fold the dough in half and again press it into a 3/4-inch thick rectangle. Repeat this 2-3 more times.
When you have pressed the dough into a 3/4-inch thick rectangle for the last time, you are ready to cut out your biscuits. Press a 3-inch biscuit cutter (or upside down glass) straight down into the dough without twisting. Cut out as many biscuits as you can and place them on the parchment-lined baking sheet. It is ok if the biscuits are close together.
Reshape the dough scraps to cut out more biscuits.
Brush the tops of the biscuits with a little bit of heavy whipping cream. Sprinkle with turbinado sugar, if desired.
Bake for 13-16 minutes, or until biscuits are golden on top.