There are 3 layers of graham crackers, 5 layers of cream filling, and 2 layers of blueberry sauce. You can break the graham crackers up to fit the pan.

Whisk the cornstarch, lemon juice, and warm water together in a small bowl until the cornstarch has dissolved. Set aside. Warm the blueberries and sugar together in a small saucepan over medium heat. Stir continuously for about 3 minutes, until the blueberries begin to release their juices. Add the cornstarch mixture and continue stirring for another 2–3 minutes, smashing some blueberries as you go. The mixture will begin to thicken. Remove from heat and stir in the lemon zest. Set aside to cool completely (place in the fridge to speed it up).

Line a 9×5-inch loaf pan with plastic wrap with overhang over the edges to easily lift the cake out. Set aside.

Using a hand mixer or stand mixer fitted with a whisk attachment, whip the cold heavy cream on medium-high speed until soft peaks form, about 3 minutes. Transfer to another bowl. Using the same mixing bowl, beat the cream cheese on high speed until completely smooth and creamy, about 1 minute. Add the confectioners’ sugar, lemon juice, and lemon zest and beat until combined and creamy. Gently fold in the whipped cream. Do not over-mix.

Spread a couple Tablespoons of cream filling into a very thin layer in the bottom of the prepared pan. This will help the bottom layer of graham crackers stick. Place some of the graham crackers in a single layer on top (break them to fit). Spread about 3/4 cup (approx. 130g) of cream filling on top of the graham crackers. Then layer half of the blueberry sauce on top, another 3/4 cup of cream filling, another layer of graham crackers, 3/4 cup of cream filling, the rest of the blueberry sauce, 3/4 cup of cream filling, the rest of the graham crackers, and, finally, the rest of the cream filling.

Cover with plastic wrap and/or aluminum foil and place in the freezer for at least 4 hours or overnight.

Before serving, allow the cake to soften in the refrigerator for 1 hour or at room temperature for 10–15 minutes. Lift the cake from the pan using the overhang on the sides. Garnish with fresh blueberries, mint, and/or lemon slices. Cut into slices and serve cold.

Cover and store leftovers in the refrigerator or in the freezer. If frozen, allow to soften again before eating.