For the Dough
- 1/ 3 cup granulated sugar
- 2/ 3 cup whole milk or unsweetened oat milk
- 3 tablespoons vegetable oil
- 3 1/ 2 cups all-purpose flour
- 1/ 2 ripe sourdough starter
- 3/ 4 teaspoon kosher salt
- 3 large eggs
- 1 teaspoon vanilla bean paste or vanilla extract
For the Filling
- 3/ 4 cup black sesame paste or tahini
- 1/ 2 cup granulated sugar
- 1/ 4 cup black and white sesame seeds
- 1 mandarin orange, zested
- 1/ 2 cup raspberry jam
For the Glaze
- 1/ 3 cup granulated sugar
- 1/ 3 cup water
- 1 strip mandarin orange peel
- 1/ 2 teaspoon vanilla extract
- 3 tablespoons black and white sesame seeds
- Freeze-dried raspberries, crushed
Make the dough
Heat sugar, milk, and vegetable oil in a small pot over low heat, stirring occasionally, just until sugar is dissolved. Remove from heat and allow to cool slightly.
Add milk mixture to the bowl of an electric mixer and stir in eggs with dough hook attachment until well combined. Stir in half the flour until a sticky paste forms, then add remaining flour and ripe sourdough starter.
Scrape down sides of bowl as necessary, then increase speed to medium-low and knead for about 12 minutes, until a small piece of dough can stretch into a thin sheet without tearing (also known as the windowpane test). Transfer dough to a lightly greased bowl, then cover with a damp towel and allow dough to rest for 30 minutes.
Using a lightly wet hand, gently stretch and fold each side of the dough up and over itself into the center. Allow dough to rest for an additional 30 minutes, then perform one more set of folds. Cover bowl and let rise at room temperature (about 72F degrees) until dough has risen about 1/4 and small bubbles appear on the surface, about 4 hours. Cover tightly and refrigerate 18-24 hours. Dough should have risen to double its original volume with lots of bubbles along the bottom.
Fill and Shape Buns
Line two baking sheets with parchment paper.
Stir black sesame paste with granulated sugar until well combined.
Roll dough to 1/4" thick on a floured surface, using extra flour as needed to prevent sticking. Dough should be about 14" x 22".
Spread black sesame mixture over dough in an even layer, then sprinkle with sesame seeds and mandarin orange zest. Carefully fold dough in half, pressing to adhere. Cut dough into 10 equal strips using a sharp knife.
Working one at a time, gently stretch one strip of dough to about 14" long. Twist each end in opposite directions. Take one end and form into a spiral, tucking the end under itself. Transfer to prepared baking sheet. Repeat with remaining dough, then allow to proof for 2 hours at warm room temperature (you can create this warm environment by turning the light on in your oven).
Make the glaze
Meanwhile, simmer water, sugar, vanilla extract, and mandarin orange peel in a small pot over medium heat until syrupy, about 8 minutes.
Fill and Bake Buns
Preheat oven to 350F degrees (don't forget to remove the proofing buns from the oven if they are in there!)
Gently deflate the center of each proofed bun and fill with about 1 tablespoon raspberry jam. Bake until golden brown, about 22-24 minutes.
Brush buns with one coat of glaze immediately after removing from oven.
Allow to cool slightly, then brush with more glaze and sprinkle with sesame seeds and crushed freeze-dried raspberries.
These buns are best the day they are baked, but will keep at room temperature in an air-tight container for 2 days. Gently reheat before serving for best texture.