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caramelized white chocolate buttercream pumpkin bars

Megan
moist and fluffy brown butter pumpkin bars topped with creamy caramelized white chocolate buttercream. the ultimate fall dessert!
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Prep Time 1 hour 20 minutes
Cook Time 35 minutes
Cooling Time 35 minutes
Total Time 2 hours 30 minutes
Course Celebrations, Dessert
Cuisine American
Servings 24

Equipment

  • stand mixer with paddle attachment
  • 9X13 baking pan
  • parchment paper
  • baking sheet

Ingredients
  

brown butter pumpkin bars

  • 2 c all purpose flour (240g)
  • 1 teaspoon baking soda
  • 1 tsp baking powder
  • 1 tbsp pumpkin pie spice (see notes)
  • ½ teaspoon salt
  • 1 c unsalted butter (227g), browned and cooled to room temperature (170g) (see notes)
  • 1 c packed light brown sugar (220g)
  • ¼ c sugar (50g)
  • 3 large eggs, room temperature
  • 1 c pumpkin puree

caramelized white chocolate mascarpone buttercream + toasted walnuts

  • 6 oz. caramelized white chooclate (150g) (see notes)
  • 1 c unsalted butter, softened (113g)
  • 8 oz. mascarpone cheese, room temperature
  • 2 ½ c powedered sugar, sifted
  • 1 tsp vanilla bean paste (alt. use vanilla extract)
  • ½ tsp salt
  • ⅓-1/2 c crushed walnuts, lightly toasted

Instructions
 

brown butter pumpkin bars

  • To make the brown butter, melt butter in a clear heavy bottom pot. Once the butter starts to foam, whisk continuously until brown bits start to form. Remove from heat, pour into clean bowl, skim the foam from the top and cool to room temperature (30 minutes).
  • Line 9x13 baking pan with parchment paper and preheat oven to 350F. Whisk together flour, baking powder, baking soda, salt and pumpkin spice. Set aside.
  • In a stand mixer with paddle attachment, browned butter, and sugar until smooth and well combined. Add eggs, beating well after each one until well combined. Add pumpkin puree and vanilla bean paste, beating until well combined.
  • Add dry ingredients to the wet ½ batch at a time. Slowly beat each time until JUST combined. A few flour streaks is okay! Drop evenly sized scoops into the prepared pan. Evenly press batter/dough into the pan.
  • Bake at 350 for 35-45 minutes or until a toothpick inserted into the center comes out clean or with a few moist crumbs. Pull from the oven, and allow to cool min. 60 minutes. Pumpkin bars should be completely cool before frosting.

caramelized white chocolate mascarpone buttercream

  • Return caramelized white chocolate to liquid form by placing in a microwave safe bowl and heating in 20 second intervals (stirring after each) until melted. Cool to room temperature.
  • In a stand mixer, with paddle attachment, beat butter until light and fluffy, about 4-5 minutes. On the lowest speed, beat in the mascarpone cheese with butter until well combined. Go slowly or you risk the cheese breaking. Once combined, slowly beat in cool (but still liquid) caramelized white chocolate. Add powdered sugar, a generous tablespoon at a time, beating slowly to combine. After adding about half the powdered sugar, add in the salt and vanilla bean paste. Beat until well combined. Add the remaining half of the sugar, a generous tablespoon at a time, beating until well combined. Once all the sugar is added, beat frosting on med-high until smooth. Using a palette knife or spatula, spread frosting on top of cooled pumpkin bars.
  • To toast walnuts, line walnuts on a parchment lined baking sheet. Bake in oven at 350F for 8-10 minutes. Cool and roughly chop. Scatter on top of frosting.

Notes

pumpkin pie spice: Feel free to use a store bought version if you have one you like. If you'd like to make a homemade version, here is my preferred version: 
⅓ c ground cinnamon (32 g)
2 ½ tablespoon ground ginger (15 g)
2 teaspoon ground nutmeg (4g)
1 teaspoon ground allspice (4g)
½ teaspoon ground cardamon (1g)
Mix all ingredients together in a small mixing bowl. Store in an airtight container such as spice jar or small glass mason jar. 
browned butter: water evaporates from the butter while it is browning, accounting for the change in weight. If using melted butter, aim for ¾ c or about 170g.
caramelized white chocolate: its preferred to use homemade for this, as you can adjust the level of caramelization to your tastes, however, it does require some advanced planning and about an hour of prep time. Worth it in my opinion. You can also use store bought, "golden" white chocolate which is basically the same thing. 
Keyword caramelized white chocolate, celebration, mascarpone, sheet cake, spiced
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