Preheat oven to 350 degrees F. Mix together water, oatmeal and ¾ cup butter. Cover with towel and let stand for 20 minutes.
Beat together the eggs, white sugar and 1 ½ cups brown sugar and 1 ½ teaspoons vanilla in a large bowl. In a medium bowl, combine flour, salt, cinnamon, nutmeg, baking powder and baking soda. Add to egg-sugar mixture. Now add water-oatmeal-butter mixture to it.
Pour cake mixture into lightly greased 9×13 baking dish and bake in preheated oven for 35-40 minutes, or until a toothpick inserted into the center of it comes out clean. Let cake cool.
For the topping, add coconut flakes, 1 teaspoon vanilla, cream, ½ cup butter and ¾ cup brown sugar to a medium saucepan. Stir and bring to a boil. Let boil for one minute. Let cool and spread onto cooled cake.