The raspberry sauce must cool down completely before using, so I recommend making it first. Mix 1 teaspoon water with 1 teaspoon cornstarch in a very small bowl. Set aside. Combine raspberries, granulated sugar, and remaining 1 teaspoon of water together in a small saucepan over medium heat. Stir the mixture as it begins to cook, breaking up some of the raspberries as you stir. Once simmering, add the cornstarch mixture. Continue to stir and allow to simmer for 3 minutes. Remove the pan from heat and press through a fine mesh strainer to remove the seeds. Allow the thin raspberry sauce to cool completely before using. Cover and store for up to 1 week in the refrigerator.

Preheat oven to 350°F (177°C). Line the bottom and sides of a 9-inch square baking pan (8-inch is too small) with parchment paper, leaving an overhang on the sides to lift the finished bars out (makes cutting easier!). Set aside.

In a food processor or blender, pulse 22 Oreos (including the cream filling) into a fine crumb. You should have about 2 cups (packed) crumbs, or 250g. Pour crumbs into a large bowl. Add the melted butter and stir to combine. The mixture will be thick and quite wet. Try to smash/break up any large chunks. Pour the mixture into prepared pan. With medium pressure using your hand, pat the crumbs down into the bottom to make a compact, thick crust. Bake for 8 minutes. Remove from the oven and set aside. Leave oven on.

Melt the chopped white chocolate in a double boiler or the microwave. If using the microwave: place the white chocolate in a medium heat-proof bowl. Melt in 20 second increments in the microwave, stirring after each increment until completely melted and smooth. Let the warm chocolate cool as you work on the other cheesecake filling ingredients. You can place it in the refrigerator, but just don’t let it solidify!

Using a handheld or stand mixer fitted with a paddle attachment, beat the cream cheese and granulated sugar together on medium-high speed in a large bowl until the mixture is smooth and creamy, about 2 minutes. Add the flour, lemon juice, vanilla extract, and salt, then beat until fully combined. On medium speed, add the eggs one at a time, beating after each addition until just blended. After the 2nd egg is incorporated into the batter, stop mixing. A few small lumps can remain. Pour in the cooled (but still liquid) white chocolate. Beat on low speed just until combined.

Pour half of the cheesecake filling onto the crust. It’s ok if the crust is still slightly warm. Drizzle half of the raspberry sauce all over the top. Spread remaining cheesecake filling on top. (It’s ok if the raspberry sauce has spread to the sides or slightly incorporates into the top layer of cheesecake.) Drizzle remaining raspberry sauce on top, then use a toothpick or knife to gently swirl everything together.

Bake for 32–36 minutes or until the cheesecake appears set on top and the edges are lightly browned. The bars will be puffy, but will sink slightly down as they cool. Place pan on a wire rack. Cool for 45 minutes at room temperature, then chill in the refrigerator for at least 3 hours (and up to 1 day) before slicing. If you plan to chill the bars for longer, loosely cover with aluminum foil after 3 hours of chilling.

To slice, lift the bars out of the pan as a whole using the parchment overhang on the sides. Cut into squares with a sharp knife. For extra neat squares, wipe the knife clean between each cut.

Cover and store leftover cheesecake bars in the refrigerator for up to 1 week.