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
• 2 1⁄2 pounds portobello or cremini mushrooms
• 1 large sweet onion, diced
• 2 ribs celery, diced
• 1 carrot, diced
• 2 sprigs fresh rosemary
• 8 sprigs fresh thyme
• 1 bay leaf
• 2 teaspoons kosher salt
• 2 quarts cold water
• 1⁄4 cup extra-virgin olive oil
• Freshly ground black pepper
• 1 cup (2 sticks) unsalted butter
• 1 cup all-purpose flour
• 2 cups whole milk
• 1⁄4 cup Worcestershire sauce
• 1⁄4 cup Texas Pete or Crystal hot sauce
• 1⁄4 cup chopped fresh flat-leaf parsley
• 1⁄4 cup chopped fresh thyme leaves
• 2 tablespoons chopped fresh rosemary leaves
• Finely grated zest and juice from 1⁄2 lemon