Preheat oven to 350 degrees F. Spray or grease a 13 x 9-inch baking pan.
Mix all dry cake ingredients in a large bowl. In a medium bowl, beat egg with milk, water and vanilla. Add the melted butter to the dry cake ingredients, then stir in the egg/milk mixture, mixing until all dry ingredients are incorporated. It is important here NOT to use an electric mixer but to mix with a spoon--the "cake" is actually a muffin base by the amount of baking powder, so it should not be "over-mixed."
Pour cake batter into prepared pan. Set aside.
In another bowl, beat the topping ingredients until they resemble a paste--for this you CAN use an electric mixer.
Drop topping randomly over top of cake batter--I did 4 rows with 3 dollops in each row, each dollop being about 2 tbs. Now pull a knife through the cake and topping, "marblizing" the topping into the top part of the cake batter.
Bake at 350 degrees F for 25-35 minutes, or until toothpick inserted in the center comes out clean. Remove from oven and cool slightly on a rack.
Mix the glaze ingredients in a small bowl, adding ONLY enough milk or cream to make a thick but pourable glaze--always start with the lowest amount of liquid.
Drizzle glaze over cake and let it set about 15 minutes. Cake may be served warm or completely cooled.
Makes about 12 servings.