Preheat oven to 350 degrees F. Line an 8x8-inch baking pan with foil, and spray generously with nonstick spray. Set aside.

Combine room temperature Butter, Brown Sugar, Oats, Flour, Graham Cracker Crumbs, Baking Soda, Salt, and Cinnamon in a large bowl. Using an electric hand mixer, mix on LOW speed until all ingredients are combined, and dough is moist and crumbly.

Press about 2/3 of the dough into a thin layer on the bottom of the prepared baking pan.

Using a greased knife or spoon and greased fingers, spread Marshmallow Crème evenly over the dough layer. This step may look a little messy, but do your best to get the marshmallow crème into a fairly even layer.

Place the chocolate pieces on top of the marshmallow layer.

Take a small piece of the remaining dough into your hands; flatten into a thin layer, and place on top of the chocolate layer. Repeat with remaining dough. The dough will not completely cover the top; the layers underneath will peek through a little bit, and this is ok!

Bake for 24-26 minutes, until crust is set and top is lightly browned.

Allow pan to cool completely on a wire rack.

Cut into bars, and lift the foil out of the pan for easy removal of the bars.

Store bars in a tightly sealed container at room temperature for up to one week.

Makes 12-16 bars