Preheat oven to 350. Butter and lightly flour three 8″ round pans. Line with parchment paper circles.
Melt butter in saucepan over medium heat. Cook, swirling occasionally, until butter turns brown. Remove from heat and let cool.
Sift together flour, baking powder, baking soda, salt and cinnamon.
In large bowl combine browned butter (including any brown bits on the bottom of pan), granulated sugar, brown sugar, eggs and vanilla bean paste. Whisk until combined.
Whisk in dry ingredients, adding in two batches.
Add sweet potato puree and mix well.
Divide batter evenly between the three 8″ round pans.
Bake for 32-36 minutes, until toothpick inserted into center comes out clean.
Let cool in pans for 10 minutes, then remove to wire rack to finish cooling.
Make the Marshmallow Buttercream:
In bowl of stand mixer, beat butter and marshmallow fluff on medium speed for 2 minutes until creamy.
Add in confectioner’s sugar 1 cup at a time, mixing and scraping bowl as necessary.
Add milk and continue to mix on medium speed 3-4 minutes until fluffy.
Make the Maple Glaze:
Combine all ingredients in a small bowl. Whisk until smooth. Use immediately.
Assemble the Cake:
Once the cakes have cooled, trim off the top so that they are level.
Place one layer of cake onto serving plate or cake stand and top with one cup of marshmallow frosting. Repeat with second cake layer, more frosting and then last layer of cake.
Crumb coat cake and refrigerate 10 minutes until set. Frost the cake and smooth the sides and top, reserving about ½ cup frosting, for garnish. Using the tip of a spatula, create swirls on sides, if desired.
Make glaze and drizzle over the top with small drips overflowing the edge. (Find more tips for pretty drips here). Wait 5 minutes for the glaze to set up a tad.
Using a large round tip, pipe dollops of frosting on top of the set glaze, sporadically but in a circular form.
Sprinkle with chopped pecans and a light dusting of cinnamon to finish.
Maple glaze should be thick yet pourable so that it flows down the side of your cake with a little resistance. Unsure if your glaze is the right consistency? Set a small bowl upside down on a larger plate and do a test drizzle onto the bowl. If it is too thick and doesn’t drip down the side, even with some assistance, add a few more drops of milk to loosen the glaze. If it is too thin and runs right off the side of the bowl and pools onto the plate beneath, add a little more confectioners’s sugar to thicken the glaze. Find more tips for pretty drips here.
Maple glaze should be used right after whisking, as it will harden as it dries. If needed, cover bowl of prepared glaze with a damp paper towel to prevent it from setting. Whisk again before using.
Milk can be substituted for the light corn syrup in the maple glaze, if desired. However the glaze will not have the same shine.