Preheat your oven to 350°F (175°C). Line a standard 12-cup muffin tin with paper liners and set aside.

Place the butter in a small saucepan over medium heat. Cook, stirring often, until the butter foams and turns a golden brown color with a nutty smell. Remove from the heat and let it cool for a few minutes.

In a medium mixing bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, nutmeg, and ginger until the spices are evenly distributed.

In a large bowl, combine the browned butter, oil, eggs, brown sugar, vanilla, and sweet potato puree. Whisk until the mixture is smooth and fully blended.

Add the dry ingredients to the wet mixture and gently fold with a spatula until just combined. Be careful not to overmix - stop as soon as no streaks of flour remain.

Divide the batter evenly among the prepared liners, filling each one about three-quarters full. Bake for 22-25 minutes, or until a toothpick inserted in the center comes out clean. Let the cupcakes cool completely on a wire rack.

Top each cupcake with a spoonful of marshmallow fluff. Then press mini marshmallows into the fluff in a single layer so they hold in place.

Using a butane torch, lightly toast the marshmallows until golden brown, creating a topping similar to sweet potato casserole.

Serve right away or store in an airtight container until ready to enjoy.