Preheat oven to 350°. Stir together first 3 ingredients in a small bowl, using a fork. Sprinkle in a greased and floured 12-cup Bundt pan.
Whisk together flour, baking soda, and salt.
Beat butter, brown sugar, granulated sugar, and vanilla at medium speed with a heavy-duty electric stand mixer 3 to 5 minutes or until fluffy. Add eggs, 1 at a time, beating just until blended. Add flour mixture alternately with buttermilk, beginning and ending with flour mixture. Beat at low speed just until blended after each addition, stopping to scrape bowl as needed. Beat in chocolate mini-morsels. (Mixture will be thick.) Spoon batter into prepared pan.
Bake at 350° for 50 to 55 minutes or until a long wooden pick inserted in center comes out clean. Cool in pan on a wire rack 10 minutes; remove from pan to wire rack, and cool completely (about 1 hour). Garnish, if desired.