Allow butter, cream cheese, and eggs to stand at room temperature for 30 minutes. Meanwhile, grease and lightly flour a 10-inch fluted tube pan or two 8x4x2-inch loaf pans, set aside.

Preheat oven to 325 degrees F. Combine flour and baking powder; set aside.

In a mixing bowl beat butter and cream cheese with an electric mixer on medium to high speed for 30 seconds. Gradually add sugar, beating about 6 minutes or until very light and fluffy. Beat in vanilla. Add eggs, one at a time, beating 1 minute after each addition and scraping bowl frequently. Add flour mixture, beating on low to medium speed just until combined. Pour batter into prepared pan, spreading with the back of a spoon or small spatula, if necessary, to form an even layer.

Bake for 60 to 65 minutes for tube pan or 65 to 70 minutes for loaf pans or until a wooden toothpick inserted near center comes out clean. Cool in pan(s) on wire rack 10 minutes. Remove from pan(s); cool thoroughly on rack. Cut triangles of cake.

In a mixing bowl stir together mascarpone cheese, walnuts, milk, and honey.

To serve, arrange cake wedges in individual bowls with fruit, if desired. Add a dollop of mascarpone mixture (about 1 tablespoon per bowl). Makes 20 servings.

Prepare mascarpone mixture up to 2 days ahead; cover and chill.