In a large bowl, whisk together the warm milk, yeast, and 1/2 tsp sugar and let it rest until fluffy for 5-7 min.

In a large bowl (preferably of a stand mixer), add the flour, the remaining sugar, salt, eggs, butter, vanilla, and the activated yeast.

Mix them well until combined for about 3-4 minutes. Then, cover it with a cloth or plastic wrap and let it rest at room temperature for 4-5 minutes.

After that knead the dough with a stand mixer for 10-15 minutes until it no longer sticks edge of the bowl and is perfectly smooth.

Transfer the dough into a large bowl and cover it with plastic wrap and let it sit for 30-45 minutes until almost doubled in size. Then place it in the refrigerator and let it rest for 1 1/2 hours.

In a medium saucepan, add blueberries, sugar, lemon zest, and lemon juice and bring them to a boil while stirring constantly over medium heat. Using a potato masher, mash the blueberries. Then turn the heat over to medium-low heat and cook for 8-15 minutes stirring occasionally until it has a thick and jammy texture. Remove from the heat and let it cool to room temperature.

Place the dough onto a lightly floured surface and roll the dough into a 14×12 rectangle (around 1/4 inch thick).

Reserve 1 tbsp of the blueberry puree for frosting, and using a spatula evenly spread the remaining puree over the dough. Sprinkle ground ginger evenly if you prefer.

Starting from the long end, roll the dough down to the bottom edge.

Using a string or sharp knife cut the dough into 8-9 equal rolls. Place the buns on baking sheets or a cast iron skillet lined with parchment paper and cover it with a clean kitchen towel. Let it rest for 40-45 min at room temp.

Preheat the oven to 350F. Bake the buns for about 25-30 minutes. Remove them from the oven and let them cool for 20 min.

Prepare the frosting: In a medium bowl, add cream cheese, butter, powdered sugar, blueberry pure, vanilla, and salt. Using an electric whisk, mix until smooth. Spread on cooled rolls, and serve immediately.