Preheat the oven to 425?F. Lightly grease a 12? cast iron skillet or large round baking pan with butter. Set aside.

In a large bowl, whisk together the cake flour, all-purpose flour, sugar, baking powder, baking soda, and salt.

Add in the cubed butter, and use a pastry cutter or two knives to cut the butter into the flour mixture until it resembles pea-sized chunks.

Make a well in the center of the mixture, and pour in the buttermilk and sourdough discard. Mix with a wooden spoon until barely combined.

Use your hands to knead and fold the dough over itself a couple of times until combined.

Add the blueberries, and gently fold a few more times until the blueberries are evenly dispersed.

Use a very large cookie scoop or a ? cup measuring cup to scoop the dough for each biscuit, and place in the prepared skillet or pan.

Mix together the brown sugar and cinnamon in a small bowl for the topping.

Brush the tops of the biscuits with buttermilk or heavy cream. Then, sprinkle the tops with the cinnamon sugar mixture.

Bake for 20-25 minutes, or until fluffy and golden brown.

While baking, prepare the whipped salted vanilla bean butter by whipping the butter and vanilla bean paste together in a medium bowl until combined and fluffy.

Remove the biscuits from the oven and serve warm with the whipped salted vanilla bean butter, honey, and flaky sea salt if desired.