Pour the boiling water over the oatmeal and let stand for 20 minutes.
Preheat oven to 350 degrees.
To the oatmeal, add the 1 cup brown sugar (lightly packed), 1 cup white sugar, 1/2 cup butter, flour, nutmeg, cinnamon, salt, baking soda and eggs. Mix well.
Pour into a greased one-layer (9 x 13") cake pan.
Next, make the topping. The topping is baked along with the batter.
To make the topping, in a saucepan put the chopped walnuts (or use pecans), 9 Tablespoons butter, 3/4 cup brown sugar, flaked sweetened coconut, and 1 1/2 teaspoons vanilla. Heat over low heat just until everything is well blended and the butter has melted. (This topping is doubled from how my Mom used to make it.).
Drop the topping over the cake batter with a spoon.
Bake for 45 minutes or until the cake tests done when a toothpick is inserted.