Place the butter in a small saucepan and melt over medium heat. Once the butter is almost completely melted add the sugar in ½ cup-fulls at a time, stirring to incorporate fully after each addition. Add the salt and stir to combine.

Transfer the sugar mixture to a large mixing bowl and add the vanilla and cocoa powder. Stir until the cocoa is completely incorporated, the mixture will be very thick.

Add the eggs to the batter and mix until the batter has thinned out and is shiny.

Stir in the flour and the baking powder completely.

Now add the prepared sweet potato and chopped nuts. Stir to combine.

Pour the batter in the prepared pan, spreading to the edges.

The brownies can be baked at this point or continue with the following steps to add the swirls.

In a small mixing bowl combine the almond butter, confectioner’s sugar, softened butter, vanilla, milk, and salt. Stir until combined and completely smooth.

On top of the prepared brownie batter in the pan, alternate dollops of the almond butter mixture and the marshmallow fluff all over the top of the brownies. Drag the tip of a butter knife through the batter, creating swirls.

Bake for 38- 40 minutes until the top of the brownie has set, is starting to crackle, and the swirls have puffed up on top. A cake tester or toothpick inserted in the center should come out fairly clean with only a few crumbs attached.

Transfer the pan to a wire rack to cool completely. Use the parchment sling to easily remove the brownies from the pan. Cut into 16- equal sized squares or wedges.