This easy-to-bake recipe is my childhood dream: a mix of all the things other kids had in their lunch boxes (Little Debbie oatmeal pies! Marshmallow fluff!). The frosting is even better the second day. —Posie (Harwood) Brien
In a large skillet or saucepan, melt the butter over medium heat. Swirl it constantly until the butter begins to brown and dark solids appear--it will start to quickly smell nutty. Remove it from the heat and whisk in all the spices, then set aside to let cool to room temperature.
Preheat the oven to 350 degrees F. Butter an 8" x 8" baking pan (I like to line it with parchment for good measure).
Add the egg, brown sugar, molasses, vanilla, and salt to the cooled butter and beat until light in color and well-mixed.
Fold in the oats and the flour. Pour the batter into your prepared pan and bake for 25 minutes. Remove from the oven and let cool while you prepare your frosting.
Beat the softened butter until fluffy, then add the confectioners' sugar and keep beating until pale in color.
Add the marshmallow cream, vanilla, and salt and beat until light and fluffy.
Spread over the bars, cut into squares, and serve!