01 -
Heat blueberries, brown sugar, and lemon juice in a saucepan over medium-high heat for about 20 minutes, stirring now and then. Once the berries start getting thick and jammy, mix the cornstarch with water until smooth, then stir this slurry into the bubbling fruit. Keep cooking while stirring constantly for 2 more minutes. Save 1-2 tablespoons of this gorgeous jam for your frosting later, then pour the rest into a bowl to cool down.
02 -
Whisk water and flour together in a small pot. Cook over medium heat, whisking the whole time, for about 4-5 minutes until it becomes a thick, paste-like mixture. Scrape this into a bowl and let it cool while you work on other things.
03 -
Combine flour, sugar, yeast, and salt in your stand mixer bowl. Add the egg, milk, vanilla, and your cooled tangzhong. Use the dough hook on low speed for 2 minutes until everything comes together into a shaggy dough ball.
04 -
With the mixer still running on low, add the soft butter bit by bit - about half a tablespoon at a time. Let each addition fully disappear into the dough before adding more. Once all the butter is in, keep kneading for 8-10 minutes until the dough looks silky and stretches easily. The dough should stick to the bottom but not climb up the sides - adjust with flour or milk if needed.
05 -
With buttered hands, shape the dough into a smooth ball by pulling the edges down and under. Place it seam-side down in a buttered bowl, cover with plastic wrap, and let it puff up in a warm spot for about an hour until it doubles in size.
06 -
Roll the risen dough on a floured surface into a 20x15-inch rectangle with the long side facing you. Mix together brown sugar, butter, and cinnamon until smooth. Spread this cinnamon mixture evenly over the dough, leaving a half-inch border at the top. Then spread your cooled blueberry jam over the cinnamon layer.
07 -
Roll the dough up tightly from the bottom, then pinch the seam to seal. Use a sharp serrated knife or dental floss to slice the log into 12 even pieces, each about 1½ inches thick. Arrange them in a parchment-lined 9x13 pan.
08 -
Cover the pan with plastic wrap and let the rolls rise for 45-60 minutes until they're puffy and touching each other. Meanwhile, heat your oven to 325°F. Bake for 23-26 minutes until the tops are golden brown, then cool on a wire rack.
09 -
Beat together cream cheese, butter, and powdered sugar until fluffy and smooth. Whisk in the heavy cream and your reserved blueberry jam until you have a gorgeous purple-streaked frosting. Spread generously over the warm rolls and dive in!