Combine flour, baking powder, sugar, and salt in a mixing bowl. Whisk to combine.
Use a food processor or grater to grate frozen butter. Add grated butter to flour mixture. Mix butter and flour together, until it resembles small crumbs.
Use a fork to smash 1/3 of the blueberries then toss all of the blueberries into the flour. Mix to distribute blueberries throughout the flour.
Add very cold buttermilk to the flour and stir/knead this until the milk is fully incorporated. Form a ball of dough (it will be slightly wet) then empty the dough onto a floured surface. Add more flour on top of the dough and continue kneading for 60 seconds.
Lightly coat a rolling pin with flour and use it to roll out to a rectangle that is approximately 9x12”. Use a biscuit or cookie cutter to make uniform biscuits.
Spray baking sheet with nonstick spray or smear butter onto the pan before baking. Bake for 20 - 25 minutes, depending on the size of the biscuits and your preferred doneness. The larger your biscuits, the longer they will take to bake.
To make the glaze
Whisk together powdered sugar, milk, vanilla extract, and lemon juice. Drizzle over warm biscuits.