Preheat oven to 325 degrees F. Grease and flour a 6-cup Bundt pan or an 8½- x 4½-inch loaf pan. Set aside.
Combine cocoa, 1 tablespoon SPLENDA® Sugar Blend, and baking soda; gradually stir in hot water to form a paste. Set aside.
Combine flour, SPLENDA® Sugar Blend, baking powder, and salt in a large mixing bowl. Cut butter into flour mixture with a fork or a pastry blender until crumbly. (This procedure may be done with a mixer at the lowest speed. Cover mixing bowl with a clean tea towel to prevent spattering).
Combine eggs, milk, and vanilla in a small mixing bowl; add 1/3 of the egg mixture to flour mixture. Beat at low speed of an electric mixer until blended. Beat at medium speed for 30 seconds or until batter is smooth, stopping to scrape down sides of bowl. Repeat procedure 2 times. Set aside half of the batter. Add cocoa mixture to remaining batter, beating at low speed until blended. Alternate light and dark batters by tablespoonful’s into prepared pan. Gently swirl batters with a knife to create a marble effect.
Bake 45 to 50 minutes or until a wooden pick inserted in center comes out clean. Cool in pan on a wire rack 10 minutes. Remove from pan; cool completely on a wire rack. Drizzle with chocolate glaze, if desired.
Glaze Directions: microwave cream in a glass measuring cup at HIGH 30 seconds or until hot. Add chocolate morsels; stir until smooth. Place mixture in a small heavy-duty zip-top plastic bag. Snip a tiny hole in 1 corner of bag, and drizzle chocolate over cake.