Preheat oven to 350℉. Line a 9x9 baking dish with foil or parchment paper. Set aside.

Add graham crackers to a food processor and process until it becomes small crumbs. Transfer crumbs to a mixing bowl. Add melted butter and sugar and mix until well combined.

Press into bottom of baking dish evenly. Bake for 10 minutes. Leave oven on.

Add cream cheese to bowl of a stand up mixer with beater attachment and beat until creamy and smooth. Add condensed milk and mix until combined.

Add egg yolks one at a time, mixing well after each addition.

Add lime zest, lime juice, and vanilla extract and mix until combined.

Pour over graham cracker crust and smooth out with a rubber spatula. Bake for 15-18 minutes or until set. When you give the baking dish a shake, the bars should wiggle just a bit. You do not want the top to brown.

Chill in the fridge for 4 hours.

Meanwhile, add blackberries to a food processor and pulse until coarsely chopped. Store in fridge until ready to use.

Prior to serving, cut bars and top with chopped blackberries and lime zest if desired.