How to Make It
Preheat oven to 425°F. Prepare the Biscuits: Whisk together spelt flour, baking powder, and salt in a medium bowl. Cut in butter with a pastry blender or 2 knives until mixture resembles coarse meal. Add buttermilk; stir just until moist. Turn dough out onto a lightly floured surface. Pat into a 1-inch-thick square; cut into 12 square biscuits.
Prepare the Filling: Heat 2 tablespoons of the oil in a large skillet. Sprinkle turkey with 1 teaspoon of the salt and 1/2 teaspoon of the pepper. Add turkey to skillet, and cook, stirring occasionally, 3 to 4 minutes. Remove from skillet. Add remaining 1 tablespoon oil; add Brussels sprouts, mushrooms, carrots, onion, and thyme; cook, stirring constantly, until onions are translucent, 6 to 8 minutes.
Whisk together flour and 1/2 cup of the stock in a small bowl until smooth; set aside. Add remaining 2 1/2 cups stock, 1/2 teaspoon salt, and 1/2 teaspoon pepper to vegetables in skillet. Bring to a boil over high. Stir in flour mixture; boil 2 minutes. Stir in turkey.
Pour mixture into an 8-inch-square glass baking dish. Top with biscuits. Brush biscuits with 1 tablespoon of the melted butter. Bake in preheated oven until biscuits are set, 10 to 12 minutes. Brush biscuits with remaining 1 tablespoon butter. Bake until biscuits are golden brown and filling is bubbly, 5 to 7 minutes. Let stand 10 minutes before serving.