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S'Mores Boston Cream Pie

5 from 24 votes
Prep Time 45 minutes
Cook Time 35 minutes
Total Time 1 hour 20 minutes
Servings 12 slices
Calories 394
This twist on a classic screams S'Mores! Graham cracker cake sandwiches the best chocolate pastry cream and gets topped with a marshmallow creme frosting.

Ingredients

Pastry Cream:

  • 475 grams whole milk (1¾ cups plus 3 Tablespoons)
  • 125 grams sugar (⅔ cup less 2 teaspoons)
  • 1 Tablespoon Dutch process cocoa
  • 1 large egg
  • 2 large egg yolks
  • 25 grams flour (3 Tablespoons)
  • 25 grams cornstarch (3 Tablespoons plus 1 teaspoon)
  • 142 grams bittersweet or semi-sweet chocolate*, finely chopped (5 ounces)
  • ½ teaspoon vanilla extract

Cake:

  • 100 grams graham cracker crumbs (¾ cup)
  • 60 grams all purpose flour (½ cup)
  • teaspoons baking powder
  • ¼ teaspoon flaky sea salt
  • 1 Tablespoon vanilla extract
  • 2 large eggs (at room temperature)
  • How to Make S'Mores Boston Cream Pie
  • 200 grams sugar (1 cup)
  • 120 grams whole milk (½ cup)
  • 71 grams unsalted butter (5 Tablespoons)

Marshmallow Crème Frosting:

  • 2 large egg whites
  • 100 grams sugar (½ cup)
  • 55 grams light corn syrup (2 Tablespoons plus 2 teaspoons)
  • ¼ teaspoon cream of tartar
  • teaspoon salt
  • 2 teaspoons vanilla

Instructions 

Pastry Cream

  • Line a baking sheet with a long piece of plastic wrap. Alternatively, set aside a heat proof bowl and a piece of plastic wrap.
  • In a medium saucepan, combine the milk, half the sugar (approximately 63 grams), and the cocoa powder. Over a medium heat, bring the mixture to a simmer, stirring occasionally.
  • In a heatproof bowl, whisk together the remaining sugar, eggs, egg yolks, flour and cornstarch, until it is thick and pale in color.
  • Whisking constantly, pour approximately one-half of the heated milk mixture into the egg mixture. Pour the tempered egg mixture back into the pan with the rest of the milk. Heat over medium heat, whisking constantly. Once the mixture start to boil, set a timer for 2 minutes and continue whisking constantly. At the two minute mark, remove the pan from the heat and immediately add the chocolate and the vanilla, whisking until the chocolate is fully melted and mixed in. If the mixture has some scrambled eggs in it, push it through a strainer onto the prepared baking sheet lined with plastic wrap. If the mixture appears smooth, there is no need to strain it. Immediately cover the pastry cream entirely with the plastic wrap and allow it to come to room temperature before using. The pastry cream can be made up to three days ahead and stored in the refrigerator until you are ready to use it. (You can use it directly from the refrigerator.)

Cake

  • Preheat the oven to 350° F. Grease an 8-inch round cake pan with non-stick spray. Line the bottom with parchment paper and spray the bottom of the parchment paper with non-stick spray.
  • In a small mixing bowl, whisk together the graham cracker crumbs, flour, baking powder and salt. Set aside.
  • Place the eggs and the sugar in the mixing bowl of a stand mixer. With the whisk attachment, beat the eggs and sugar on medium speed for 5 minutes, then increase to high speed for an additional 4-5 minutes. The mixture will be pale and thick and will hold its shape for at least several seconds when dropped on itself.
  • While the eggs and sugar are whisking, combine the milk and butter in small saucepan and heat over low heat, stirring occasionally to help the butter melt, just until the mixture comes to a simmer. Turn the heat off and stir in the vanilla.
  • Set the mixer to the lowest speed and add the dry ingredients, just until almost fully combined. With the mixer still running on the lowest speed, slowly pour the hot milk mixture into the batter and continue mixing just until all ingredients are fully combined. Use a spatula to scape the sides of the bowl and to ensure the batter is fully mixed. Pour the batter into the prepared pan.
  • Bake for 33-36 minutes. The cake should be lightly brown on top and a toothpick inserted in the center should come out clean. Allow the cake to cool in the pan for 15 minutes before using a metal spatula or knife to release it from the sides of the pan. Invert the cake onto a wire rack to cool completely.

Marshmallow Creme Frosting

  • Fill a medium size pot about one-third with water. Place the pot on a burner over medium-low heat. In the metal bowl of a stand mixer, combine all ingredients except for the vanilla. Place the bowl over the pot of water. The water should not touch the bottom of the mixing bowl.
  • Constantly whisk the mixture until it reaches 160° F. If using pasteurized egg whites, you can go to just 140° F. Do not stop whisking, as you do not want scrambled egg whites. Once the mixture reaches the correct temperature, immediately remove the mixing bowl from the heat and insert it onto the mixer with the whisk attachment. Whisk at medium-high speed until stiff peaks form. (Start mixing immediately. The mixture will cool as it is whipped.) Add vanilla and whisk an additional 30 seconds until fully incorporated.

Assembly

  • Slice the cake in half so you end up with two layers. Set aside the top half (which was on the bottom of the pan before you inverted it to cool).
  • Place the chocolate pastry cream into a mixer (or use a hand mixer) to beat the pastry cream for a minute or two. Spread the pastry cream evenly on top of the bottom layer of the cake. Place the other half of the cake on top of the pastry cream.
  • Pipe or spread the marshmallow creme frosting on top of the cake. If desired, carefully use a kitchen torch to brown the frosting.

Notes

*I have also used half milk chocolate and half unsweetened chocolate and achieved a wonderful result. Play around with different chocolate combinations. 
You can make the pastry cream up to one day in advance. Store it wrapped with plastic wrap on its surface in the refrigerator. When ready to assemble the cake, beat the cold pastry cream directly from the refrigerator and spread on the cake.
You can also make the cake one day in advance. Once cooled, wrap in plastic wrap and store in the refrigerator until you are ready to assemble.
Calories: 394kcal
Course: Dessert
Cuisine: American
Keyword: marshmallow frosting, pastry cream

Nutrition

Calories: 394kcal | Carbohydrates: 62g | Protein: 6g | Fat: 14g | Saturated Fat: 7g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 4g | Trans Fat: 1g | Cholesterol: 93mg | Sodium: 222mg | Potassium: 212mg | Fiber: 2g | Sugar: 48g | Vitamin A: 337IU | Calcium: 114mg | Iron: 2mg