Step 1

Line a 9-by-5-inch loaf pan with plastic wrap, making sure the entire pan is covered and has at least 2 inches of overhang.

Step 2

Scoop 2 pints of the vanilla ice cream into a large bowl. Stir until spreadable. Fold in the blackberry preserves until combined. In a medium bowl, scoop the remaining 1 pint of vanilla ice cream and stir until spreadable. Fold in ¼ cup of the lemon curd.

Step 3

Working quickly, sprinkle the bottom of the prepared loaf pan with ½ cup of the crushed cookies. Dollop 1 cup of the blackberry ice cream mixture over the wafers. Top with ½ cup of the lemon curd ice cream mixture, swirling and spreading to smooth. Gently press ½ cup of the blackberries into the ice cream. Repeat the layers twice, ending with a final layer of the crushed cookies.

Step 4

Wrap the entire loaf pan with plastic wrap. Freeze until the cake is firm, 6 hours or up to 1 week.

Step 5

To a large bowl, add the heavy cream, 1/2 cup of the lemon curd, and the vanilla. Using an electric hand mixer, whip at medium-high speed until stiff peaks form, 2 to 4 minutes. Cover and refrigerate until ready to use, up to 1 hour.

Step 6

Remove the icebox cake from the freezer. Using the plastic overhang, remove the cake from the loaf pan and invert it onto a serving platter. Dollop with the lemon whipped cream and top with blackberries.

Step 7

Slice and serve with dollops of the remaining lemon curd, if desired.