Mix together oats and boiling water and set aside.

Cream together the white sugar 1 cup brown sugar, and shortening.  Add the eggs; mix well.  Add the oatmeal mixture; mix well.  Sift together the flour, soda, salt and cinnamon.  Add to the oatmeal mixture; mix well.  Bake in a greased and floured 13 x 9 cake pan for 25 to 30 minutes at 350 degrees. 

Topping - Mix together the margarine, 2/3 cup brown sugar, nuts, coconut, milk, and vanilla.  Boil 3 minutes.  Spread on cake immediately.  This cake is even better after it sits a couple of days, so make it ahead of time!

This is one of the best cakes I've ever eaten.  It's moist and delicious!