Buttered Pecan Biscuits

Name: Buttered Pecan Biscuits
Ingredients: 1 cup pecan halves, coarsely chopped; 3 tablespoons unsalted butter; 3 cups all-purpose flour; 2 1/2 teaspoons baking powder; 1/2 teaspoon baking soda; 1/4 teaspoon freshly grated nutmeg; 3/4 teaspoon salt; 1/4 cup packed light brown sugar; 3/4 (1 1/2 sticks) cup cold unsalted butter, but into small cubes; 1 large egg, lightly beaten; 3/4 cup cold buttermilk, plus more for brushing the biscuits; 2 teaspoons pure vanilla extract; turbinado or granulated sugar for sprinkling on top before baking