In a stand mixer, whip the cream until soft peaks form, then set aside. In a large bowl, beat the creme fraiche, milk and pudding mix until thickened. Fold in the whipped cream and set aside.
Place half of the cubed pound cake in the bottom of the trifle dish. Arrange a third of the strawberries, blackberries and blueberries over the cake. Top with half of the pudding mixture. Repeat with the remaining pound cake, another third of berries and the remaining pudding. Top the final layer of pudding with the remaining berries. Refrigerate for 2 hours. Just before serving, garnish with lemon zest and a sprig of mint.