Preheat the oven to 350.

In the bowl of a food processor, add graham crackers and pulse until fine crumbs. Pour in the melted butter and run the machine until the crumbs are evenly coated and can be pinched together.

In a mixing bowl, add the apple butter and pumpkin purée along with the dark brown sugar, evaporator milk, eggs, and spices. Whisk together.

Line a 9 x 9 square baking dish with parchment paper. Add the butter graham cracker crumbs and press firmly into the bottom. Pour pumpkin mixture over top.

Bake in preheated oven for 45 to 50 minutes. Cool to room temperature.

In a clean mixing bowl, add the egg whites. Using a hand mixer, beat to soft peaks. Add the marshmallow fluff in batches, raise the mixer speed to high and whip to stiff peaks. Spoon into a piping bag (fitted with a pastry tip if desired).

Pipe the meringue over the top of the pumpkin pie bars (conversely, you can just spoon it on and spread it over the top, using a spoon or offset spatula to create swirls and peaks). Use a kitchen torch to brûlée the surface (or place briefly under broiler).