To make the jam, add blackberries for the jam to a food processor. Process until the berries are chopped.

Add chopped berries to a medium saucepan. Stir in sugar and lemon juice, then bring to a boil over medium-high heat. Stir the jam occasionally, cooking until thickened, about 10 minutes. Let cool to room temperature.

Use plastic wrap to line a 9-inch by 5-inch loaf pan. Make sure that the plastic hangs over the edges on all sides. Set aside.

Add mascarpone for the cake to a stand mixer and beat on medium-high speed with powdered sugar and lemon zest. Beat until fluffy, about 4 minutes total.

Gradually beat in cream on low speed. Increase speed to medium and beat until soft to medium peaks form.

Add one third of the mixture to a small bow, cover with plastic wrap and place in the refrigerator for later. Add the honey to the remaining two-thirds of the lemon cream until just incorporated.

To assemble the cake, add a layer of graham crackers to the bottom of the prepared pan. Break the pieces up as needed to fit. Add a quarter of the lemon honey cream over the graham crackers. Spread it into an even layer.

Add 1/2 cup of the jam on top, spreading carefully over the cream. Drizzle with 1/4 cup lemon curd.

Spread 1/3 of the remaining lemon honey cream over the curd, top with a layer of graham crackers. Top with half the remaining cream, 1/2 cup ja,, and remaining lemon curd. Add a final layer of lemon honey cream and top with graham crackers. Cover the cake with plastic wrap, then freeze for at least 6 hours. Place the remaining jam in an airtight container and place in the refrigerator.

When ready to serve the can, invert the cake on serving platter and carefully remove the plastic wrap. Use the leftover lemon cream you put in the refrigerator to coat the outside of the cake. Chill for 15 minutes in the freezer.

Mix remaining blackberries in with the jam and spoon over the top of the cake. Serve chilled.