1. Heat oven to 350°F. Grease and flour 12-cup fluted tube pan. Place 1 cup milk chocolate chips in medium microwave-safe bowl. Microwave at MEDIUM (50%) 1 minute; stir. If necessary, microwave at MEDIUM an additional 15 seconds at a time, stirring after each heating, until chips are melted when stirred.
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 melted chocolate; beat until blended.
3. Stir together flour, cocoa, baking soda and salt; add to chocolate mixture alternately with buttermilk, beating until blended. Add syrup and vanilla; beat until blended. Stir in remaining milk chocolate chips and pecans. Spoon batter into prepard 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. Sprinkle with powdered sugar, if desired. 12 to 16 servings.
*To sour milk: Use 1 tablespoon white vinegar plus milk to equal 1 cup.