Best Buttermilk Biscuits and Mushroom Gravy

Ingredients

• 6 1⁄2 cups flour
• 3 tablespoons sugar
• 2 tablespoons plus 2 teaspoons baking powder
• 1 tablespoon kosher salt
• 1 1⁄2 teaspoons baking soda
• 1 1⁄2 cups (3 sticks) unsalted butter, diced and chilled
• 3 cups buttermilk, chilled
• 2 tablespoons butter, melted