How to Make It
Line bottom and sides of an 8 1⁄2- x 4-inch loaf pan with plastic wrap, allowing 4 to 5 inches to extend over all sides.
Beat 1⁄2 cup of the heavy cream with an electric mixer on high speed until soft peaks form. Gently stir lemon juice into softened strawberry ice cream, and gently fold in whipped cream. Spread mixture into prepared pan, smoothing with a small offset spatula. Freeze 1 hour.
Beat remaining 1⁄2 cup heavy cream on high speed until soft peaks form. Gently fold whipped cream into softened mango sorbet. Spread mixture over strawberry mixture in loaf pan, smoothing with a small offset spatula, and sprinkle with cookie crumbs.
Pull excess plastic wrap at sides tightly over cake, gently pressing down on cookie crumbs. Freeze 4 to 24 hours.
Lift semifreddo from pan, using plastic wrap as handles, and transfer, crumb side down, to a serving plate. Garnish with diced mango and sliced strawberries. Cut semifreddo into 8 slices, using a serrated knife dipped in hot water and wiped dry.