• Line a 9x5-inch loaf pan with plastic wrap, leaving enough overhang on all sides to lift the cake out later. Set aside.

Make the blueberry sauce

• In a small saucepan, combine the blueberries, granulated sugar, and lemon juice. Cook over medium heat, stirring occasionally, until the blueberries soften and release their juices, about 5 minutes.
• In a small bowl, mix the cornstarch and water to make a slurry. Stir the slurry into the blueberry mixture. Reduce to a simmer and cook until the sauce has slightly thickened, about 2-3 minutes.
• Remove from heat and stir in the lemon zest. Transfer to a bowl and refrigerate until completely cool, about 45 minutes.

Make the mascarpone mixture

• In a medium bowl, use a spatula to cream together the mascarpone, powdered sugar, lemon juice, lemon zest, vanilla, and salt. Set aside.

Make the whipped cream filling

• In the bowl of a stand mixer fitted with the whisk attachment, whip the heavy cream on low speed, gradually increasing to medium-high, until stiff peaks form, about 2-3 minutes. Use a spatula to gently fold the mascarpone mixture into the whipped cream until no streaks remain.

Assemble the cake

• Helpful tip: These instructions are easier than they look. I highly suggest you refer to the step-by-step photos in the recipe post above this recipe card!
• Using a small offset spatula, spread about 1/4 cup of the whipped cream mixture in a thin layer over the bottom of the prepared pan. Arrange 3 graham cracker halves on top, overlapping slightly if needed to fit.
• Spread a heaping 1/2 cup of the whipped cream evenly over the crackers. Top with one-third of the lemon curd (about 3 tablespoons), one-third of the blueberry sauce (about 1/2 cup), and a heaping 1/2 cup of the whipped cream mixture, spreading each layer evenly before adding the next. Arrange another layer of graham cracker halves over the whipped cream, adding additional pieces as needed to cover the surface.
• Repeat step 9 two more times, finishing with a thick layer of whipped cream on top.
• Cover the top of the cake with plastic wrap and refrigerate for at least 4 hours, or overnight.

Finish the cake

• Once chilled, transfer to the freezer for 20 minutes to make it easier to unmold.
• Just before the 20 minutes is up, in the bowl of a stand mixer fitted with the whisk attachment, whip the heavy cream, starting on low speed and gradually increasing to medium-high, until soft peaks form, about 1-2 minutes. Add the powdered sugar and continue beating until stiff peaks form, about 1 minute more.
• Remove the cake from the freezer. Uncover the top, then gently loosen the plastic wrap around the edges of the pan. Carefully invert the cake onto a serving plate or platter. Remove the loaf pan and plastic wrap from the cake.
• Using a small offset spatula, spread the whipped cream over the entire cake in an even layer, covering all the edges as if you were frosting a cake. Use the tip of the spatula to make some swirls into the cream, if desired. Carefully set back in the freezer for an additional 30 minutes so it’s easy to slice.
• Remove from freezer and sprinkle with crushed graham crackers, then slice and serve.
• Storage:

  Fridge - Store any leftovers in an airtight container or wrapped in plastic in the fridge for up to 3 days. The graham crackers will soften the longer the cake sits.

  Freezer - Place leftover slices on parchment or plastic wrap in an airtight container for up to 1 month. Thaw in the fridge before serving. The graham crackers will soften completely as the cake freezes and thaws, creating a light, fluffy texture throughout. I haven't tested freezing the cake whole.