Preheat oven to 375˚F.

In a medium-size bowl, combine powdered sugar, egg yolk and butter. Whisk until well combined. Add vanilla and flour and stir until all flour is incorporated.

Press into the sides and bottom of a 9 or 10-inch tart pan. I like to start on the sides and form a nice even layer, then work the rest of the dough into the bottom of the pan. Prick lightly with a fork and freeze for at least one hour.

Remove from freezer and press a sheet of foil tightly into the bottom and against the sides of the crust. Bake for 15 minutes, then remove foil and prick the bottom of the crust lightly with a fork again. Return to oven and bake another 13-15 minutes or until light golden brown. Remove from oven and allow to cool.

Place lemon juice in a small microwave-safe bowl. Sprinkle gelatin on top and stir. Allow to sit for 5 minutes. Mixture will be thick and gelatinous. Place in microwave and cook on high power for 15 seconds. Set aside.

In the bowl of an electric mixer, combine cream cheese and lemon zest. Beat for 2 minutes until very fluffy. Slowly add condensed milk, stopping several times to scrape the sides of the bowl. Continue beating for another minute.

Slowly add gelatin mixture while continuing to beat. Beat for 2 more minutes, stopping once to scrape the sides of the bowl. Pour into cooled shortbread crust and spread to an even layer. Refrigerate for at least 2 hours.

Place marmalade in a small microwave-safe bowl. Heat on high power for 1 minute. Pour through a fine mesh strive, pushing on solids with the back of a spoon. Discard solids.

Combine strained marmalade, blueberries and blackberries in a medium size bowl and stir to combine. Spoon fruit mixture over lemon layer. Refrigerate for 2 hours. Remove from refrigerator 20-30 minutes before serving. Garnish with fresh mint leaves, if desired.