How to Make It
Preheat oven to 450°F. Line a rimmed baking sheet with parchment paper; set aside.
Grate cold unsalted butter using a box grater, or cut butter into small pieces. Cover and freeze 10 minutes.
Sift flour into a large bowl; whisk in baking powder, salt, baking soda, and 1/4 cup of the sugar. Using a pastry cutter or your fingers, cut frozen butter into flour mixture. Make a well in the middle of flour mixture, and add buttermilk; gently stir until mixture forms a shaggy dough. Add strawberries, and stir just until strawberries are incorporated. Do not overmix.
Turn dough out onto a well floured surface. Using a rolling pin, roll dough into an 11- x 9-inch rectangle. Fold long ends into thirds, and roll again into an 11- x 9-inch rectangle. Repeat folding and rolling 2 times, ending with rolling dough into a 1-inch-thick rectangle. Using a 2 1/2-inch round cutter, cut 12 rounds from dough. Place dough rounds on prepared baking sheet. Bake in preheated oven until lightly browned and set, 10 to 12 minutes.
Remove biscuits from oven. Brush evenly with melted salted butter, and sprinkle evenly with remaining 1 teaspoon sugar.