In a bowl, combine flour and pecans. Stir in butter. Press into a greased 13-in. x 9-in. baking dish. Bake at 350° for 12-14 minutes. Cool on a wire rack.
Place the sweet potatoes in a large saucepan and cover with water; bring to a boil. Cover and boil for 15 minutes or just until tender; drain and mash. Add sugar, butter and extracts; stir until smooth. Spread over crust.
For topping, beat cream cheese and sugar in a bowl until smooth. Fold in whipped topping. Spread over filling. sprinkle with pecans if desired. Refrigerate for 4-6 hours.