Preheat oven to 350° F. Lightly spray a 9" pie pan with non-stick spray.

In a large bowl, beat butter and sugar until combined. Add egg and vanilla, and beat again until combined. Add flour, graham cracker crumbs, baking powder, and kosher salt. Beat just until combined.

Press slightly more than half of the mixture into the bottom and up the sides of prepared pie pan. The crust mixture can be sticky, so I like to keep a tablespoon of butter beside me, to dip my finger tips in as I press in the crust.

Spread marshmallow creme evenly over the bottom crust. Break 4 of the whole chocolate bars into individual pieces (smaller rectangles) and lay them evenly over the top of the marshmallow creme. Top with one cup of the mini marshmallows.

With the remaining crust mixture, portion small to medium-sized jagged clumps. Do not press the crust mixture together; touch it as lightly as you can to keep its jagged texture. Drop clumps over the top of the marshmallows, taking care to not pat in the crust mixture. Take a look at the pre-baked pie photos in this post, to see what the top crust mixture should look like. Add the remaining 1/2 cup of mini marshmallows over the top. Then break the remaining whole chocolate bar into individual pieces and poke them randomly into the top of the pie.

Bake for 18 to 20 minutes, or until nicely browned. Remove pan from oven and let cool on a wire rack. Let pie cool completely before cutting for the cleanest cuts. If you cut the pie while it's still warm, it will be very gooey and messy. When I want very nice, clean-cut pieces, I will refrigerate the pie for about 30 minutes after it has cooled to room temperature. And when I really don't care what the pieces look like, and I just want a gooey, chocolatey treat, I eat the pie while it's still warm. It's all up to you. :)