Blueberry Lemon Poppy Seed Rolls

Light and fluffy blueberry lemon poppy seed rolls with a brioche lemon poppy seed dough, blueberry curd, and a lemon mascarpone frosting.

Add the flour and 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 milk, sugar, yeast, egg, flour, salt, butter, and tangzhong 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 the bottom of the bowl, and passes the windowpane test.*
Once the dough is done kneading, zest a large lemon into the dough and add in the poppy seeds. Mix until well combined.
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 curd.

Prep a small mixing bowl by adding the cubed butter to it, along with a fine mesh sieve. Set aside.
Add the sugar to a small saucepan, then zest the lemon into the pan. Use your fingers to rub the zest into the sugar.
Juice the lemon, and add 20g (1 tbsp. + 1 tsp.) of lemon juice to the saucepan. Then add in the egg, salt, and blueberries. Vigorously whisk the mixture to break up the egg.
Set the saucepan over medium heat, stirring constantly (this can be slowly – we just need constant movement happening!)
Continue to stir the curd until it thickens and reaches a temperature of at least 170°F / 76°C (This takes me about 3-5 minutes.)
Remove the curd from the heat and pass it through the fine mesh sieve, over the butter. Mix the curd and the butter together until the butter has melted and the mixture is smooth.
Transfer the curd to the freezer to chill until you're ready to assemble the rolls. (If you're assembling the rolls the next day, keep the curd in the fridge.)

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 120g (½ c.) of the chilled blueberry curd over the dough into an even layer. Store the remaining blueberry curd in the fridge. Cut the dough into 6 long strips, then roll them up. (This will be messy!)
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°F / 175°C. (Optional:) Make an egg wash by whisking together an egg with 1 tbsp. milk, then brush it over the rolls.
Bake for ~20-25 minutes, until the tops of the rolls are golden brown and the internal temperature of the rolls has reached 200°F / 93°C.

Add the mascarpone, lemon zest, sugar, and salt to a small mixing bowl. Beat (by hand or with a mixer) just until the ingredients are combined.
Add in the heavy whipping cream and beat the mixture until soft peaks form.
Once the rolls have cooled to room temperature, top them with the lemon mascarpone frosting and extra blueberry curd & enjoy!