Proof the yeast: warm ½ cup of the milk to 90°F to 100°F (32°C to 38°C), like warm bath water. Stir in 1 tsp of the sugar and 2 tsp active dry yeast, and let it sit about 10 minutes, or until it foams up. A tall, fluffy foam means strong yeast (Note 2).

Combine the dough: in the bowl of a stand mixer, add 3 cups bread flour, the rest of the sugar, the remaining ½ cup warm milk, 1 large egg, 1 large egg yolk, 2 Tbsp sour cream, 1 Tbsp vanilla extract and the yeast mixture. Mix with the dough hook until a rough, shaggy dough forms.

Knead the dough: knead on low (speed 2 to 3) for about 20 minutes, until the dough stops sticking to the sides of the bowl, feels elastic and passes the windowpane test (Note 3). Stop once it is elastic, since over-kneaded dough tears and cannot hold a good rise.

Add the butter and salt: add 3 oz unsalted butter and ½ tsp kosher salt and knead 5-7 minutes, until no streaks of butter remain. Tearing the dough into chunks helps the butter mix in faster.

Let the dough rise: shape the dough into a smooth ball by tucking the edges under. Set it in a large oiled bowl, cover loosely and let it rise somewhere warm and draft-free, about 80°F (27°C), until doubled, about 1½ hours. If it more than doubles, punch it down and keep going (Note 4).

Soak the blueberries: while the dough rises, cover 1 cup dried blueberries with warm water for about 10 minutes. Drain them and blot them dry with paper towels.

Punch down the dough: press the air out gently and turn it out onto a well-oiled counter.

Roll out the dough: roll the dough into a 24 x 12-inch rectangle. Roll gently so you keep the air bubbles.

Fill the dough: scatter 1 cup dried blueberries and 1 cup white chocolate chips over it, leaving a 1-inch strip bare along one long edge. Press them in lightly.

Roll it up: roll the dough up tightly like a jelly roll, with no air gaps. Pinch the seam shut and let it rest seam side down for 5 minutes.

Stretch the roll: place both hands in the middle and roll it back and forth while moving your hands out toward the ends, until it is twice as long and half as thick.

Twist into a wreath: fold the rope into a V and twist the two strands around each other, starting at the fold. Tuck the loose ends into the loop and pinch to close the ring.

Let the wreath rise: set the wreath on a baking sheet lined with parchment paper, cover loosely with a towel and let it rise until almost doubled, about 1 hour. With the filling in, it can take longer (Note 4).

Heat the oven: about 20 minutes into the second rise, heat the oven to 350°F (175°C) with a rack in the middle (Note 5).

Brush with egg wash: beat 1 large egg with 1 pinch kosher salt and brush it over the risen wreath, all the way into the twists.

Bake the wreath: bake at 350°F (175°C) for about 35 to 40 minutes, until the crust is deep golden brown, a toothpick in the center comes out clean and the inside reads 190°F to 195°F (88°C to 91°C). If the top browns too fast, tent it loosely with foil (Note 6).

Cool the wreath: cool on a rack for at least 30 minutes before slicing.

Glaze the wreath (optional): whisk 1 cup powdered sugar, 1½ Tbsp whole milk and ½ tsp vanilla extract until smooth and pourable, and drizzle over the cooled wreath.