Pour the melted butter into a 9x13 baking pan. Set aside.
Add the sugar, flour, salt, and baking powder in a medium bowl. Whisk to combine.
Add in the half and half and vanilla extract in with the dry ingredients. Whisk until combined. It will be very runny.
Pour the topping batter into the pan on top of the butter.
Pumpkin Filling
In a large bowl, add the pumpkin puree, evaporated milk, eggs, 1 cup granulated sugar, brown sugar, flour, and spices. Whisk until combined.
Pour the pumpkin filling over the top of the topping mixture in the pan.
Dot the top of the pumpkin filling with the cubed butter and sprinkle with the remaining 4 tablespoons of granulated sugar. The crust will rise to the top as it bakes.
Place the cobbler in the preheated oven and bake for approximately 1 hour, until a toothpick inserted into the center comes out clean and the top is browned.
Once done, cool the cobbler on a wire rack.
Once cooled, scoop into dessert dishes and top with the marshmallow glaze and pecan halves.
Marshmallow Glaze
For marshmallow topping, add the powdered sugar, half and half, vanilla, and marshmallow fluff in a large bowl. Beat with a hand mixer on medium until smooth.
Notes
You can substitute the half and half for milk in this recipe.If you don't have pumpkin pie spice on hand, use ⅓ teaspoon each of gound ginger, ground cloves and ground nutmeg and ¾ teaspoon of ground cinnamon