1. Make the Blueberry Jam Filling:

• In a medium saucepan, combine the frozen wild blueberries, brown sugar, and lemon juice. Cook over medium-high heat for about 20 minutes, stirring occasionally.
• As the berries begin to break down and thicken, dissolve the cornstarch in water, then stir it into the blueberry mixture.
• Continue cooking for an additional 2 minutes, stirring constantly, until the mixture thickens into a jam-like consistency.
• Set aside 1-2 tablespoons of the jam to use later for the frosting. Transfer the rest to a bowl and let it cool completely.

2. Prepare the Tangzhong:

• In a small saucepan, whisk together the water and all-purpose flour. Cook over medium heat, whisking constantly for 4-5 minutes, until the mixture thickens into a paste-like slurry.
• Remove from heat and scrape the tangzhong into a bowl. Let it cool before adding it to the dough.

3. Make the Cinnamon Roll Dough:

• In the bowl of a stand mixer, combine the all-purpose flour, granulated sugar, yeast, and salt. Mix on low speed until the dry ingredients are fully combined.
• Add the egg, room-temperature milk, vanilla extract, and cooled tangzhong to the dry ingredients. Mix with the dough hook attachment on low speed until a dough starts to form.
• Gradually add the softened butter, half a tablespoon at a time, allowing each portion of butter to fully incorporate before adding more.
• Once all the butter has been added, continue kneading the dough on low speed for about 8-10 minutes, until it becomes smooth and elastic. The dough should stick slightly to the bottom of the bowl but pull away from the sides.
• If the dough is too sticky, add extra flour one tablespoon at a time. If it’s too dry, add half a tablespoon of milk as needed.
• With lightly buttered hands, remove the dough from the bowl and shape it into a smooth ball. Place the dough in a large, lightly buttered bowl, cover it with plastic wrap, and let it rise in a warm place for about 1 hour, or until doubled in size.

4. Assemble the Cinnamon Rolls:

• Once the dough has risen, punch it down gently and transfer it to a lightly floured surface.
• Roll the dough into a 20×15-inch rectangle, keeping the long edge closest to you.
• In a small bowl, mix the dark brown sugar, softened butter, and ground cinnamon to create the cinnamon-sugar filling.
• Spread the cinnamon-sugar mixture evenly over the rolled-out dough, leaving a small border around the edges.
• Spoon the cooled blueberry jam over the cinnamon-sugar mixture, spreading it evenly across the surface.
• Starting from the long edge closest to you, carefully roll the dough into a tight log. Pinch the seams to seal.

5. Cut and Bake the Rolls:

• Using a sharp knife or dental floss, cut the log into 12 equal-sized rolls.
• Arrange the rolls in a greased 9×13-inch baking dish, leaving some space between each roll to allow for expansion.
• Cover the rolls with plastic wrap and let them rise in a warm place for another 30-45 minutes, or until they are puffed and nearly doubled in size.
• Preheat the oven to 350°F (180°C) during the second rise.
• Bake the rolls for 25-30 minutes, or until golden brown on top and fully cooked through.

6. Make the Cream Cheese Frosting:

• In a medium bowl, beat together the room-temperature cream cheese and unsalted butter until smooth and creamy.
• Add the powdered sugar and mix until fully combined and fluffy.
• Stir in the reserved blueberry jam and heavy cream, mixing until the frosting is smooth and has a spreadable consistency.

7. Frost and Serve:

• Once the rolls are done baking, remove them from the oven and allow them to cool for about 10 minutes.
• Spread the blueberry cream cheese frosting generously over the warm rolls.
• Serve the rolls warm for the best texture and flavor.