Special equipment: a 2 1/2-inch dough cutter
Preheat a convection oven to 375 degrees F.
Using two knives, your hands or a bench scraper, cut 8 tablespoons of the butter into the flour until the mixture resembles grated Parmesan. Add 1 cup of the sugar to the mixture and combine until incorporated throughout. Gently fold in 2 cups of the blueberries, trying not to smash them!
Add the vanilla to 1 1/2 cups of the buttermilk and then add to the flour, a little bit at a time, and mix until the dough is sticky and wet (but not sloppy), and all of the loose flour from the bottom of the bowl is incorporated. Add up to 1/2 cup more buttermilk if needed. Use a bench scraper to separate the dough from the sides of the bowl. Sprinkle some flour between the dough and the bowl. Dust the table and the top of the dough liberally with more flour, then scoop out the dough onto the table.
Using a rolling pin, roll the dough out to about 2 inches thick. Dip a 2 1/2-inch dough cutter in some flour and then, starting around the outside edge of the dough, cut out the biscuits. Work your way around the outside edge of the dough, ending in the center of the dough.
Place the biscuits very close together on a parchment-paper-lined baking sheet; biscuits need to touch each other to rise properly. There should also be no room between the biscuits and the edge of the pan. After the first round of biscuits, gently bring the dough back together without kneading. Continue rolling the dough and cutting out biscuits until all of the dough is used up.
Butter the top of the biscuits generously with the remaining 2 tablespoons butter. Bake for 30 minutes.
Toss the remaining 2 cups blueberries with the remaining 1/4 cup sugar and the simple syrup. Top each biscuit with 2 tablespoons frosting and 3 to 4 blueberries, and then serve.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.