Toss 2 ½ cups raspberries with 1 tablespoon raspberry liqueur and 1 teaspoon sugar.
Toss 2 cups blueberries with 1 teaspoon lemon zest, juice of half of the lemon, and 2 teaspoons sugar. (Save remaining ½ cup raspberries and ½ cup blueberries for topping the icebox cake)
Beat mascarpone cheese, remaining 2 tablespoons sugar, and vanilla extract together in a large bowl to combine.
Slowly stream in the heavy cream and beat on low speed to combine. Gradually increase speed to medium-high and beat until medium peaks form, about 5 minutes. Feel free to use a stand mixer if you’d prefer!
To assemble the icebox cake, begin by spreading ½ cup whipped mascarpone cream evenly onto the bottom of an 8-inch by 10-inch dish.
Top with four graham crackers, breaking crackers as needed to fill any gaps. Evenly spread with 1 cup of mascarpone cream, top with raspberries and another layer of mascarpone cream. Repeat layering with remaining ingredients ending with a layer of mascarpone cream.
Top your beautifully layered No Bake Berry Icebox Cake with reserved berries and serve!