In a medium saucepan, combine 4 cups of blackberries with ½ cup of water over medium heat. Allow the mixture to simmer for about 10 minutes, occasionally mashing the berries until soft.

Strain the mixture through a fine mesh sieve to extract the juice, returning the liquid back to the pan.

To the strained blackberry juice, add ¾ cup of sugar and 1 tablespoon of lemon juice, stirring well to combine. Bring the mixture to a gentle boil, then reduce the heat and let it simmer for 5 minutes.

Once done, remove from heat and let it cool completely to room temperature.

In a chilled mixing bowl, whisk 1 cup of heavy cream until stiff peaks form, about 3-5 minutes.

In a separate bowl, blend together 8 ounces of mascarpone cheese, ¼ cup of sugar, 1 teaspoon of vanilla extract, and ⅓ cup of the cooled blackberry syrup until smooth.

Gently fold the whipped cream into the mascarpone mixture, being cautious not to deflate the airiness.

Quickly dip ladyfingers into the prepared blackberry syrup, ensuring they are just moistened but not soggy.

In a 9x13 inch baking dish, layer half of the dipped ladyfingers on the bottom. Spread half of the mascarpone cream mixture over the ladyfingers, then repeat with another layer of dipped ladyfingers and finish with the remaining cream mixture on top.

Cover the assembled Blackberry Tiramisu with plastic wrap and refrigerate for at least 6 hours, or preferably overnight.

When ready to serve, garnish with fresh blackberries or a drizzle of the remaining blackberry syrup for an eye-catching finish. Slice into squares and enjoy.