For the graham cracker layer: Preheat oven to 350 degrees F. Grease and line an 8-inch square baking pan with parchment, leaving a 1-inch overhang on each side.
Add the graham crackers, cinnamon, chili powder and salt to a food processor and pulse to break up. Add the butter and pulse until the ingredients are combined and the mixture resembles sand. Press the mixture into the prepared baking pan. Refrigerate while you make the brownie layer.
For the brownie layer: Combine the eggs, sugars and vanilla extract in a large bowl. Mix until well combined. Add the melted butter, cocoa powder, flour, baking powder, cinnamon, ancho chile powder and salt. Stir to combine, but take care to not overmix. Add the chocolate chips and fold in.
Spread the entire brownie layer mixture over the top of the graham cracker crust. Bake until the top is dry and firm, about 40 minutes. (A cake tester will not come out clean because the brownies are so fudgy!) Let them cool completely.
For the marshmallow frosting: Turn the oven to the broil setting. Adjust the oven rack so it's 6 inches from the heat source.
Spread the mini marshmallows on an unlined sheet tray, then broil until toasty and charred, about 1 minute. (As an alternative, use a kitchen torch and char until you have your desired level of darkness.) Let cool to touch.
Add the butter and powdered sugar to a bowl and beat until fluffy and well mixed. Add the marshmallow creme and vanilla and stir until combined. Set aside.
Spread the marshmallow frosting over the top of the cooled brownie. Add the charred mini marshmallows all over.
Remove from the pan and cut into squares.
Chilling slightly before cutting will make it easier to slice.