1. Heat oven to 350°F. Grease and flour 10-inch tube pan or 12-cup fluted tube pan.
2. Beat butter in large bowl until creamy; gradually add granulated sugar, beating on medium speed of mixer until well blended. Add eggs, one at a time, beating well after each addition. Add chocolate; beat until blended.
3. Stir together flour, baking soda and salt; add to chocolate mixture alternately with buttermilk, beating until blended. Add syrup and vanilla; beat until blended. Stir in pecans. Pour batter into prepared pan.
4. Bake 1 hour and 15 minutes or until wooden pick inserted in center of cake comes out clean. Cool 10 minutes; remove from pan to wire rack. Cool completely. Sift powdered sugar over top and drizzle with chocolate syrup, if desired. 12 to 16 servings.
* To sour milk: Use 1 tablespoon white vinegar plus milk to equal 1 cup.