Place the mixed berries in a medium bowl. Sprinkle 2 tablespoons granulated sugar over the berries and pour 3 tablespoons liqueur or orange juice. Gently toss to combine. Let sit at room temperature for 20–30 minutes, occasionally stirring, until the berries release some juices but remain intact. This creates a syrup to flavor the trifle layers.

Prepare the Mascarpone Whip

In a chilled mixing bowl, add 2 cups cold heavy cream, 2 tablespoons confectioners' sugar, 1 teaspoon vanilla extract, and 3 ounces softened mascarpone cheese. Whip on medium-high speed with a hand or stand mixer until soft peaks form (about 2–3 minutes). Scrape the bowl and continue whipping a few seconds until medium peaks form; avoid overwhipping. Taste and adjust sweetness with a little more confectioners' sugar if desired.

Assemble the Trifle

Choose a clear trifle bowl or individual serving glasses. Begin with a single layer of chocolate cake cubes covering the bottom (about 1 cup cake cubes). Spoon about 1/3 of the macerated berries, including some of the syrup, over the cake layer. Dollop or pipe approximately 1/3 of the mascarpone whipped cream over the berries and gently spread into an even layer. Repeat layering: another 1 cup cake cubes, 1/3 berries with syrup, and 1/3 mascarpone cream. Finish with remaining 1 cup cake cubes, remaining berries and syrup, and the last of the mascarpone cream on top. This yields three cake layers and three cream layers for a classic trifle look.

Garnish

Dust the top lightly with 1 teaspoon unsweetened cocoa powder, sprinkle 2 tablespoons chocolate shavings or mini chocolate chips, and scatter 2 tablespoons toasted sliced almonds or chopped hazelnuts if using. Optionally reserve a few whole berries for the very top for visual appeal.

Chill and Serve

Cover the assembled trifle with plastic wrap and refrigerate for at least 2 hours, preferably 4 hours, so flavors meld and cake soaks slightly with syrup. Trifle can be made up to 24 hours ahead. Serve chilled with a large spoon for family-style trifle or individual spoons for cups.