Add 200 g blueberries and 2 to 3 tablespoons caster sugar to a saucepan over medium heat. Cook until the sugar melts and the berries release their juices.

Add 4 to 5 tablespoons water to the saucepan. Continue cooking over medium heat until the blueberries are soft and jammy.

Mix 1 tablespoon cornflour with 3 tablespoons water in a small bowl. Stir the cornflour slurry into the blueberry mixture.

Cook the blueberry mixture, stirring constantly, until thickened. Remove the saucepan from the heat.

Stir 1 teaspoon lemon juice into the blueberry preserve. Let the preserve cool completely to room temperature.

Pour 1 cup heavy whipping cream into a cold mixing bowl. Whisk on high speed until stiff peaks form.

Add 200 g sweetened condensed milk, 1 teaspoon vanilla extract, and a pinch of sea salt to the whipped cream. Fold gently until evenly combined.

Cut the cheesecake slice into bite-size chunks. Set the cheesecake chunks aside.

Spread half of the ice cream base into an 8 x 4-inch loaf pan. Spoon half of the cooled blueberry preserve over the base.

Scatter the cheesecake chunks over the blueberry layer. Top with the remaining ice cream base and remaining blueberry preserve.

Gently swirl the layers with a knife without fully mixing them. Freeze until firm, at least 8 hours or overnight.