Blueberry Jam:

In a small saucepan, combine blueberries and sugar. Simmer over medium heat until berries break down and mixture thickens, and temperature reaches 106° C / 225° F on a candy thermometer. (If you don’t have a thermometer, you can manually test for thread stage. See notes in post above.)

Scoop jam into a small bowl. Set aside while you prepare the brownie batter.

Brownie Batter:

Preheat oven to 330° F / 165° C. Line an 8 x 8-inch square baking tin with parchment, allowing a 1-inch overhang on all sides. Spritz lightly with cooking spray. Set aside.

In a medium saucepan, melt butter over medium heat. Whisk in granulated sugar, cocoa powder, and kosher salt. Remove from heat and cool slightly, about 5 minutes. Mixture will be thick.

Transfer mixture to a large mixing bowl. Add eggs and vanilla bean paste and whisk to combine.

With a rubber spatula, fold in the flour, followed by the chopped dark chocolate.

Set aside while you prepare the cheesecake swirl.

Cheesecake Swirl:

Add softened cream cheese to a mixing bowl or the bowl of a stand mixer, and beat on high speed until light and fluffy.

Mix in the granulated sugar, followed by egg yolk and vanilla bean paste, and continue mixing until well combined.

Mix in the lemon zest and lemon oil.

Assembly:

Spread 2/3 of the brownie batter into prepared tin.

With a teaspoon, drop cheesecake mixture over batter. Use a knife or skewer to swirl, creating a marbled pattern.

With a teaspoon, drop blueberry jam over cheesecake layer, and use a knife or skewer to swirl.

With a teaspoon, drop reserved batter over top.

Bake in preheated oven for 50-60 minutes, or until a toothpick or cake tester comes out clean.

Cool completely prior to serving.

Store leftover cheesecake brownies in the refrigerator for up to 3 days.