Activate the yeast: In the bowl of a stand mixer, whisk together the yeast, sugar and milk. Cover with a plate or plastic wrap and let the yeast bloom until foamy and fragrant, about 15 minutes.
7 g active dry yeast, 28 g sugar, 113 g milk
Make the dough: Add the egg and sourdough discard into the yeast mixture and mix with a dough hook until dissolved and no traces of egg yolk remain.
1 egg, 113 g sourdough starter
Add the flour and salt into the bowl and continue mixing until a shaggy dough forms.
240 g all-purpose flour, 6 g salt
With the mixer on, add the butter 1 tablespoon at a time, waiting until each addition is incorporated into the dough before adding more. The dough should gradually look smooth, supple and less greasy as the butter is absorbed.
56 g butter
Continue mixing for 5 minutes or until the dough looks totally smooth, clings to the hook and pulls away from the sides of the bowl. Turn the dough out on a clean work surface and knead it lightly a few times before rounding it into a tight ball.
Proof the dough: Transfer the dough to a clean, lightly-oiled bowl and cover with plastic wrap. Let the dough rise, untouched in a warm spot until doubled in volume, about 30 minutes to 1 hour, depending on the temperature of your kitchen.
Prep: Using a piece of paper towel, blot the excess moisture from your hot dogs. Set aside. Line a large baking sheet (18 by 13 inches) with parchment paper.
Assemble the buns: Using a bench scraper, divide the dough into 6 even portions. Cover the dough with plastic wrap until ready to shape to prevent the pieces from drying out.
Working with one portion of dough at a time, flatten it into an oval about 4 inches wide and roughly the same length as your hot dog. Place a hot dog lengthwise in the center of the dough, then bring the long sides together and pinch to seal. Lightly roll the dough to make sure it’s sealed. Repeat with the remaining portions of dough.
6 hot dogs
Using a chef’s knife, mark 6 evenly spaced slits along the top of the dough. Cut through the dough and hot dog at each slit, being careful not to cut through the bottom layer of dough.
Shape the buns: You can shape these buns as a flower or a long oval.
To shape the buns into a flower, gently fan the slices out into a circle. Position one piece in the center with the hot dog cut-side up, then arrange the remaining pieces around it, cut-side up to form the petals.
Top shape the buns into an oval, arrange the pieces along the center line with the hot dogs cut-side up, alternating each piece from side to side.
Final proof: Arrange the shaped buns carefully on your prepared baking sheet. Cover with baking sheet with plastic wrap and let the dough rise until puffy, about 20 to 30 minutes.
While your buns are rising, preheat the oven to 350 F. Beat the egg until no traces of egg white remain.
Bake: Brush the dough with egg wash and sprinkle scallions and sesame seeds on top. Bake for 25 to 30 minutes or until the buns are deeply golden.
1 egg, 2 scallions, 6 g sesame seeds
Transfer the buns to a wire rack and let them cool slightly before serving.
Enjoy and store: These can be enjoyed warm or at room temperature. The buns do need to be stored in the refrigerator because of the hot dogs. I’ve found that they reheat nicely in the air fryer at 325 F for 5 to 10 minutes.