Preparation Position rack in center of oven and preheat to 400°F. Combine flour, 1/4 cup brown sugar, baking powder, baking soda, and salt in large bowl; whisk to blend. Add 6 tablespoons butter; using fingertips, rub in until butter is reduced to pea-size pieces. Mix in pecans. Whisk buttermilk, egg yolks, and extract in medium bowl. Add to flour mixture. Toss with fork until dough comes together in moist clumps. Gather dough into ball. Press dough out on lightly floured surface to 8-inch round; cut into 6 wedges. Arrange wedges 1 inch apart on ungreased baking sheet. Bake until tester inserted into center comes out clean, about 16 minutes; transfer to rack. Whisk remaining 1/2 cup brown sugar, 4 tablespoons butter, and cream in heavy small saucepan over low heat until sugar dissolves. Remove pan from heat. Whisk in powdered sugar and molasses. Spread glaze over warm scones. Let stand until glaze sets, at least 30 minutes.
Preparation Position rack in center of oven and preheat to 400°F. Combine flour, 1/4 cup brown sugar, baking powder, baking soda, and salt in large bowl; whisk to blend. Add 6 tablespoons butter; using fingertips, rub in until butter is reduced to pea-size pieces. Mix in pecans. Whisk buttermilk, egg yolks, and extract in medium bowl. Add to flour mixture. Toss with fork until dough comes together in moist clumps. Gather dough into ball. Press dough out on lightly floured surface to 8-inch round; cut into 6 wedges. Arrange wedges 1 inch apart on ungreased baking sheet. Bake until tester inserted into center comes out clean, about 16 minutes; transfer to rack. Whisk remaining 1/2 cup brown sugar, 4 tablespoons butter, and cream in heavy small saucepan over low heat until sugar dissolves. Remove pan from heat. Whisk in powdered sugar and molasses. Spread glaze over warm scones. Let stand until glaze sets, at least 30 minutes.