Wash 2 cups of mixed berries gently under cool water, then pat them dry. Hull strawberries and slice them thinly, set aside a handful for garnish.

In a mixing bowl, combine 1 cup of heavy whipping cream, ½ cup of powdered sugar, and 1 teaspoon of vanilla extract. Whip on medium speed until stiff peaks form, about 3 to 5 minutes.

In another bowl, spoon in 12 ounces of mascarpone cheese and add the optional zest of 1 lemon if desired. Gently fold in the whipped cream until smooth.

Spread a generous layer of the mascarpone mixture evenly across the bottom of a serving dish, about 1 inch thick.

Layer 8 graham crackers or ladyfingers over the mascarpone mixture, breaking pieces as necessary to fit snugly.

Top the graham crackers with a generous layer of prepared mixed berries, ensuring even distribution.

Repeat the layering process by adding more mascarpone, graham crackers, and berries until filled, ending with a thick layer of mascarpone.

Cover with plastic wrap and chill in the refrigerator for at least 4 hours, preferably overnight.

Before serving, garnish with reserved mixed berries arranged as desired.