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Marshmallow Frosting + Cinnamon Buttercream (Episode 4: The Great Pumpkin Cake Series)

Prep Time 30 minutes
Cook Time 15 minutes
Total Time 45 minutes
Course: Dessert
Cuisine: American, Fall Baking

Ingredients
  

Marshmallow Frosting
  • 3 large egg whites
  • 150 g ¾ cup granulated sugar
  • 60 ml ¼ cup water
  • ½ tsp cream of tartar optional
  • 1 tsp vanilla extract
  • 45 g about 3 Tbsp marshmallow fluff
Cinnamon Buttercream
  • 225 g 1 cups unsalted butter, room temperature
  • 150 g 1 ¼ cups powdered sugar, sifted
  • 1 tsp vanilla extract or vanilla bean paste
  • 1 ½ tsp ground cinnamon
  • Pinch of fine sea salt

Equipment

  • stand mixer or handheld mixer with whisk attachment
  • Heatproof mixing bowl
  • Saucepan for double boiler setup
  • Candy thermometer for heating egg whites to 160
  • Kitchen scale for accuracy
  • Rubber spatula
  • Piping bags + tips (optional)
  • Smalll offset spatula
  • Microwave safe bowl for warming marshmallow fluff 5-8 seconds
  • Small kitchen blow torch

Method
 

  1. Marshmallow Frosting
  2. Combine ingredients:
  3. In a heatproof bowl, whisk together 3 large egg whites (≈ 90 g), 150 g (¾ cup) granulated sugar, 60 ml (¼ cup) water, and ½ tsp cream of tartar.
  4. Heat to 160°F:
  5. Set the bowl over a pot of gently simmering water. Whisk constantly until the sugar fully dissolves and the mixture reaches 160°F (71°C).
  6. Whip to stiff peaks:
  7. Transfer the mixture to a stand mixer fitted with the whisk attachment. Beat on high for 6–8 minutes until the meringue is thick, glossy, and holds stiff peaks.
  8. Add vanilla:
  9. Beat in 1 tsp vanilla extract for 5–10 seconds.
  10. Loosen marshmallow fluff:
  11. Microwave 45 g (about 3 Tbsp) marshmallow fluff for 5–8 seconds — just until slightly loosened (not hot).
  12. Incorporate fluff carefully:
  13. With the mixer on LOW, drizzle the warmed fluff in a thin ribbon over 5–10 seconds. Stop the mixer and finish folding by hand to avoid deflating the meringue.
  14. Use immediately:
  15. Best for piping, swooping, or torching.
Cinnamon Buttercream
  1. Beat butter on medium-high 3–4 minutes until pale and fluffy.
  2. Add powdered sugar, in increments fully mixing before each addition
  3. Add cinnamon, vanilla, and salt. Mix on low until combined, then whip on high 2 minutes until smooth.

Notes

Tips & Tricks

When to Add Marshmallow Fluff

Always add fluff after the meringue reaches stiff peaks.
This prevents collapse, keeps the frosting pipeable, and maintains that glossy structure.

Avoid Over-Whipping

Once the fluff is added, stir gently. Whipping aggressively will loosen the frosting.

Perfect Buttercream Texture

Whip the butter long enough to drive out air bubbles and reduce graininess.

Double buttercream batch if you want to fully frost a layer cake 

This is enough to frost a 8x8-inch sheet cake, but double if you want to fully frost any 6-inch layer cake in this frosting.


Storage

Marshmallow Frosting

  • Best used immediately
  • On cakes/cupcakes: holds for 4–6 hours at room temp
  • Not ideal for refrigeration or freezing

Cinnamon Buttercream

  • Refrigerate airtight up to 1 week
  • Freeze airtight up to 2 months
  • Bring to room temp and re-whip before using