In a large bowl, combine the oats, flour, baking soda and salt.
In a separate bowl, beat the butter for 2-3 minutes until whipped. Add brown sugar and beat for another 2 minutes. Add the eggs and vanilla and continue to beat for another 1-2 minutes.
Add the dry ingredients to the butter/sugar mixture and mix just until barely combined. Set aside while making the chocolate layer.
In a medium saucepan, mix all of the chocolate fudge ingredients together over low heat. Stir until everything is melted and smooth and then remove from heat.
Press 2/3 of the oatmeal cookie dough into the bottom of a greased 9X13 pan. Spread the chocolate fudge over the oatmeal layer and then drop the remaining oatmeal cookie dough over the top.
Bake for 20-25 minutes or until the top begins to lightly brown. Let cool completely before cutting. They can be stored and served at room temperature, but they are delicious cold from the fridge as well!