Preheat oven to 325°F.
In a small saucepan, bring the water to a boil. Remove from the heat, add the oatmeal, and let stand for 20 minutes.
In a medium bowl, cream together the brown sugar, white sugar, shortening, and eggs.
In a separate small bowl, whisk together the flour, baking soda, cinnamon, and salt, then add to the creamed mixture, stirring until well combined.
Stir in the oatmeal.
Pour into a greased 9X13 pan and bake 35-40 minutes, until a toothpick inserted in the middle comes out clean.
While the cake is baking, in a medium bowl, mix together the softened butter, cream, brown sugar, and vanilla until smooth.
Add the coconut and chopped pecans.
Spread the frosting evently over the hot cake and place under the broiler until lightly browned, only about 3-4 minutes.
Cool slightly before serving. If you can, wait a few hours before serving to allow time for the topping to soak in some.