To make the crust: Place flour, graham cracker crumbs, and sugar in a standing mixer bowl, and add the paddle attachment. Give it a quick mix to combine. Slowly add the butter cube by cube, and mix on low until it forms a wet-sand-like consistency. Alternatively you can use a pastry cutter and cut the butter into the mixture. Add the cold water one tablespoon at a time. Dough is ready when it is firm and not sticky. 

Put it all together:  There is no need to chill the dough.  Roll dough out on flat surface that has been dusted with flour. Roll out in a circle that’s about 12 inches wide all around. Add marshmallows, milk chocolate, chocolate grahams, and peanut butter cups. Gently move around the crust and fold it in to just about an inch over the filling, leaving the middle of the galette open. Keep folding the next part on top of the previous part, and so on until the entire crust is folded inward. Brush crust with egg wash. 

Bake at 350° for 25-30 minutes, or until middle is bubbly and edges are a nice golden brown. Melt peanut butter chips in microwave safe bowl on high for 60-70 seconds or until melted. Be cautious as bowl can be hot.

Whisk chips until smooth. Drizzle over warm galette. Allow to cool slightly before serving.  Serve warm, room temperature, or cold.  Store covered at room temperature for up to four days. Enjoy!