Preheat oven to 325°F. Lightly grease 2 (9-inch) round cake pans with half of the melted butter. Cover bottom of each pan with wax paper (or parchment paper); brush evenly with the remaining melted butter. Set aside

Sift together flour, baking soda and salt; set aside. Place chocolate and the cut-up butter in large microwaveable bowl. Microwave on HIGH 2 min. or until butter is melted. Stir until chocolate is completely melted; set aside.

Beat sugar and eggs in medium bowl with electric mixer on high speed 2 min. or until slightly thickened and pale in color. Add chocolate mixture; beat until well blended. Gradually add the flour mixture, beating on low speed after each addition until well blended. Scrape down side of bowl. Add buttermilk and vanilla; beat on low speed 15 sec., then beat on medium speed an additional 15 sec. (If batter is not completely blended at this point, mix by hand with a rubber spatula until mixture is well blended.) Pour evenly into prepared pans; spread with spatula, if necessary, to evenly cover bottom of each pan.

Bake on middle oven rack 30 to 34 min. or until toothpick inserted in centers comes out with fudgy crumbs. (Do not overbake.) Cool in pans 5 min. Remove from pans to wire racks; remove and discard wax paper. Cool completely. Fill and frost with BAKER'S® 225th Anniversary Fudge Icing. Refrigerate cake until ready to serve. Let stand at room temperature 30 min. before serving.