Step 1: If making the optional syrup, combine 80ml water, 2 tbsp granulated sugar, and 1 tbsp lemon juice in a microwave-safe bowl. Microwave for 30 seconds, or until sugar is dissolved. Stir and set aside to cool.
Step 2: In a large mixing bowl, combine 250g mascarpone, 250ml double cream, 3 tbsp icing sugar, and 1 tsp vanilla extract. Whip with an electric mixer until the mixture is thick and holds stiff peaks.
Step 3: Gently toss the 250g chopped strawberries and 200g raspberries with 1 tsp lemon zest. If desired, add a tiny pinch of icing sugar. Pat the berries dry with a paper towel to remove excess moisture, which helps prevent a soggy cake.
Step 4: Line the bottom of your serving tin or dish with a single layer of sponge cake or ladyfingers. If using the optional syrup, lightly brush the cake layer with it.
Step 5: Spread a generous layer of the mascarpone cream mixture evenly over the ladyfingers. Scatter about half of the prepared mixed berries over the cream layer.
Step 6: Repeat the layering: add another layer of sponge cake/ladyfingers, lightly brush with syrup (if using), then another layer of mascarpone cream, and finally the remaining berries. You should aim for 2-3 layers of each component, ending with cream.
Step 7: Finish with a thin, even layer of mascarpone cream on top, ensuring it's smooth.
Step 8: Chill the cake in the refrigerator for at least 1-2 hours, or until it is firmly set. For best results and easier slicing, an overnight chill is ideal.
Step 9: Once set, decorate the cake with extra whipped cream, fresh berries, a few mint leaves (optional), and a light dusting of icing sugar just before serving.
Step 10: Slice into cubes or wedges and serve immediately. Enjoy your homemade Easy No-Bake Berry Mascarpone Cake!