Preheat your oven to 400 degrees F.

Poke a few holes in the sweet potatoes and bake for 1 hour or until soft and tender. When the sweet potatoes are cooked, slice them in half and allow to cool.

Reduce the oven temperature to 350 degrees F.

Peel the skins away from the flesh of the sweet potato and add the sweet potato to a mixing bowl. Mash well. Mix in the brown sugar, vanilla, cinnamon, milk, butter, eggs and bourbon (if using) until fully combined.

Pour the sweet potatoes into a greased casserole dish (I used an oval).

In a bowl, combine pecans, 2 tablespoons melted butter, flour and sage. Spread the pecan topping over top of the sweet potatoes. Bake for 30-40 minutes or until the pecans are golden.

Just before the casserole is done, make the marshmallow like topping. Place egg whites, maple syrup, and cream of tartar in the heatproof bowl of an electric mixer. Set over a saucepan with simmering water. Whisk constantly until whites are warm to the touch, 3 to 4 minutes.

Remove the bowl from the water and transfer to your stand mixer. Using the whisk attachment, whip the whites until stiff and glossy peaks form, 5 minutes. Add the vanilla, and mix until combined. Use immediately. Be careful not to over whip the mixture or the whites will get clumpy. Spoon the marshmallow into a gallon size ziplock bag and snip the corner off. Pipe the marshmallow onto the casserole (or just spread over the casserole with a spatula) and then toast using a kitchen torch OR under the broiler for 30 seconds to 1 minute (watch close as the broiler works quick!). Serve warm.