Milk Bread Blueberry Sweet Rolls

Light, fluffy & buttery brioche filled with a homemade blueberry jam, and topped with a whipped mascarpone frosting.

Add the 24g flour and 100g milk to a microwave safe bowl and whisk them together. Microwave for 30 seconds, then stir and microwave for another 30 seconds. The mixture should now be a thick slurry, but if it's not, microwave it in 10 second intervals until it has thickened.

Add the tangzhong, flour, sugar, egg, butter, yeast, salt, and milk to the bowl of a stand mixer fitted with the dough hook attachment.
Knead the mixture on medium speed for ~15-20 minutes. The dough is ready when it is no longer sticking to the sides or bottom of the bowl, and passes the windowpane test.*
Once the dough is done kneading, shape the dough into a ball and place it back into the mixing bowl. Cover the mixing bowl with plastic wrap, and place it in a warm area to rise until doubled in size (~1 hr.)**
In the meantime, make the blueberry jam.

Add the blueberries, sugar, and 30g (2 tbsp.) of lemon juice to a small saucepan set over medium heat. Stir occasionally and bring to a simmer. Let the mixture simmer for 2 minutes.
In a separate small bowl, make the cornstarch slurry by whisking together the cornstarch and remaining lemon juice.
While mixing the blueberries constantly, stream in the cornstarch slurry. Continue mixing constantly until the jam thickens, then remove it from the heat. Keep the jam covered in the fridge until you're ready to assemble the rolls.

Once the dough has finished rising, lightly punch it down to remove any excess air in it. Transfer the dough to a clean and lightly floured surface, then roll it out to a 12″ x 16″ (30 x 40 cm) rectangle. If the dough keeps springing back a lot while rolling it out, let it rest for 5 minutes before continuing.
Carefully spread the blueberry jam over the dough, reserving ~2-3 tbsp. to top the rolls later. Tightly roll the dough up into a cylinder starting from the longer (16") side.
Cut the log into 6 even pieces.
Transfer the rolls to a lightly buttered and/or lined eighth sheet pan*** Lightly cover the pan with a towel, and let the rolls rise in a warm environment until doubled in size (~30 minutes).
Preheat the oven to 350℉ / 175℃.
Brush the heavy cream over the rolls. Bake for 20-25 minutes, until the tops of the rolls start to turn golden brown and the internal temperature of the rolls has reached 180℉ / 82℃.

In a small bowl, beat together the mascarpone, sugar, vanilla and salt just until combined.
Add in the heavy whipping cream and beat until soft peaks form.
Top the rolls with the mascarpone and your reserved blueberry jam. Serve, and enjoy!