The night before you want burger buns: In a stand mixer, mix the flour, salt, coconut sugar, starter, and water into the dough (will be thick and sticky).
Use a dough hook to knead the dough gently for 2 minutes. Stop the mixer and let the dough rest for 5 minutes. Do this for four to six rounds. The dough should pass the windowpane test.
Cover the dough and let it proof overnight at room temperature.
The next day: Deflate the dough by doing a round of stretch and folds in the bowl then let it rest for 5 minutes.
Gently turn the dough out onto a floured surface.
Roll and pat the dough into a log. Cut the dough into eight equal balls.
form tight balls of dough by folding the top down to the center. Working clockwise fold all the sides into the center and push them down firmly while turning the dough.
After eight or so turns, the dough should feel tight and rounded.
Pinch the bottom of the ball and roll it gently in the palm of your hand to shape it.
Place the buns on a parchment-lined baking sheet.
Cover with a tea towel and let proof for 3-6 hours or until doubled or tripled in size.
Preheat oven to 375°F.
Mix the egg yolk and milk together in a small bowl. Using a brush, lightly coat the top of each bun with egg wash. Sprinkle the buns with everything seasoning.
Bake the buns for 30 minutes.
Remove them from the oven and from the parchment paper to a wire rack to cool completely before cutting.