Step 1

For the lemon layer, in a medium saucepan, whisk together the cold water, sugar, lemon juice, cornstarch, and salt. Heat the mixture over medium heat, stirring constantly, until it begins to thicken and large bubbles pop at the surface. Continue cooking for 1-2 minutes (it's important to continue letting it simmer so it will set up as it cools).

Step 2

Remove from the heat and stir in the lemon zest and butter. Pour into a bowl, cover with plastic wrap pressed directly on the surface, and place in the refrigerator until completely cooled.

Step 3

For the crust, preheat the oven to 325 degrees. Line a 9X13-inch pan with parchment paper or foil (for easier removal and cleanup; optional). Stir together the graham cracker crumbs, sugar, and melted butter until evenly combined. Press into the bottom of the prepared pan. Bake for 10-12 minutes until lightly golden and set. Set aside to cool completely.

Step 4

For the cream filling, melt the white chocolate until just melted and smooth; don't over heat or it can seize and scorch. I use the microwave at 50% power for 1-minute increments, stirring in between. Set aside.

Step 5

Add the cream cheese to a mixing bowl and mix with a handheld electric or stand mixer until smooth and creamy, 1-2 minutes, scraping down the sides of the bowl as needed. Add the melted white chocolate (if it's overly warm, let cool until just slightly warm) and mix again until well-combined.

Step 6

Add the powdered sugar and salt and mix until evenly combined, 1-2 minutes. (See note below about the heavy cream.) Add the heavy cream to the batter and mix on medium speed until the batter is thick and creamy, 2-3 minutes.

Step 7

Spread the cream layer evenly on top of the cooled crust. Chill for 1-2 hours until the cream layer sets up a bit.

Step 8

Once the lemon layer is completely cooled, whisk to recombine and spread evenly over the cream layer. Chill in the refrigerator until the lemon layer is set up, 4-6 hours.

Step 9

Cut into squares and serve. Include a fresh lemon slice or twist, if desired.