Step 1

Remove the pound cake from its pan and line the pan with plastic wrap, leaving plenty of overhang.

Step 2

Slice the domed mound off the pound cake and set aside, then slice the remaining cake horizontally into 3 slices.

Step 3

Melt the butter in a pan over medium heat. Crumble the cake mound into crumbs. Add to the pan and toast until golden brown all over, 1 to 2 minutes. Set aside to cool.

Step 4

Mix together the blackberries, blackberry jam, lemon zest and juice in a bowl. Set aside.

Step 5

Combine the heavy cream and powdered sugar in a bowl. Whip until firm peaks form.

Step 6

Place one layer of cake in the bottom of the lined pan and press to slightly flatten. Top with a third of the blackberry mixture and a third of the whipped cream. Repeat the process 2 more times, ending with whipped cream. Loosely cover with the overhanging plastic wrap and chill in the refrigerator for 8 hours.

Step 7

To serve, carefully lift the cake from the pan and remove the plastic wrap. Top with the toasted crumbs, a few blackberries and a sprig of mint, then slice and serve.