Line a 6x10 baking dish with parchment paper (you can also use a traditional 8x12 dish, but the bars will be thinner). Pour the graham cracker mixture into the baking dish. Using your hands, press the mixture down firmly, until it’s spread evenly throughout the pan. I also recommend using the back of a measuring cup to really flatten the graham cracker layer and make sure it sticks together. Set aside.

Add the cream cheese and powdered sugar to a mixing bowl and beat until smooth (I recommend using an electronic mixer).

Add in the sour cream, lemon juice, and vanilla, and beat again until smooth. Fold in the whipped cream.

Pour the mixture over the graham cracker layer, using a spoon or spatula to spread it evenly. Place in the freezer for 6-8 hours, or overnight.

Prepare the grape topping. Add the quartered grapes to a bowl with the lemon juice, honey, and a pinch of salt. Toss gently to combine. The grapes can either be prepared at the same time as the bars (store in the fridge with the bowl tightly covered with plastic wrap), or prepare them right before cutting the bars.

Remove the bars from the freezer and let thaw slightly. Cut into 12 square bars. Top each bar with a spoonful of the grape mixture and drizzle lightly with honey. Top each bar with a sprig of rosemary.