Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch pan.
Pour boiling water over oats. Set aside.
Sift together flour, salt, soda and cinnamon. Set aside.
Cream 1/2 cup butter, sugar, 1 cup brown sugar and eggs until fluffy. Add flour mixture and mix in. Add softened oats. Pour batter into a 9x13 inch pan.
Bake at 350 degrees F (175 degrees C) for 35 to 40 minutes. Remove cake from oven. Set oven temperature to broil.
In a saucepan, combine milk, 1/2 cup butter and 1 cup brown sugar.
Heat until melted, then add coconut and chopped nuts. Spread on warm cake.