I start by adding warm milk, instant yeast, sugar, salt, and the beaten egg into the bowl of my stand mixer. A quick whisk brings everything together before the flour goes in. This step wakes up the yeast and gets the dough base ready to build on.
Next, I add in the flour and switch to the dough hook, mixing on low speed for three to four minutes. You'll notice the dough start to pull together into a shaggy mass. This is the point where the gluten begins developing, which gives brioche its signature chew.
Once the dough has come together, I drop in the softened butter one tablespoon at a time, letting each piece incorporate before adding the next. I bump the mixer speed up slightly so the butter blends in fully. The dough will look soft, glossy, and just barely sticky when it's ready.
I transfer the dough into a lightly oiled bowl, cover it, and set it somewhere warm. It needs about one to two hours to double in size. I usually use this time to make my filling and crumble so nothing goes to waste.
Once the dough has doubled, I turn it onto a clean surface without punching it down too hard. I divide it into twelve to fifteen even pieces and roll each one into a smooth ball. These will rest while I prep the filling.
In a mixing bowl, I beat the softened cream cheese until it's completely smooth. Then I add the heavy cream and vanilla extract, followed by a pinch of salt and the powdered sugar. I beat everything together until the filling is silky and lump-free.
For the crumble, I simply combine melted butter, flour, brown sugar, and cinnamon in a bowl. I rub the mixture between my palms until it forms small, sandy crumbs. This texture is what gives the buns their crunchy bite.
I place each dough ball onto a parchment-lined tray, spacing them out since they expand while baking. Using my fingers, I press an indentation into the center of each ball and stretch it into a small circle, leaving a slight rim around the edges.
I brush the edges of each bun with the whisked egg, then spoon a generous amount of the cream cheese filling into the center. I scatter blueberries over the filling and finish with a sprinkle of crumble topping around the edges.
I bake the buns at 375°F for 20 to 30 minutes, rotating the tray halfway through for even color. They're done once the edges turn a deep golden brown and the filling looks set. I let them cool for 10 to 15 minutes before digging in.