In a large mixing bowl, add the buttermilk, salt, melted butter, all purpose flour, and the bloomed yeast mixture.
Using a dough hook, knead the dough for 8 minutes.I like to use the stand mixer for 3 minutes until the dough is pulling away from the sides of the bowl and it isn't too sticky to pick up. Then, I hand knead for another 5 minutes. You may need an extra tablespoon of flour while hand kneading to get to the perfect consistency.To check, poke the dough with your finger. If the dough is soft and bounces back slowly, it's ready. Or do the windowpane test - take a small piece and slowly stretch the dough, then hold it up to a window. If light can pass through the stretched dough without it tearing, it's ready! Add some vegetable oil to a large bowl and place the dough ball inside. Using your hands, rotate the dough ball until it's completely covered in oil.
Cover with a clean kitchen towel and let it rise for two hours until it has doubled in size.
Punch the dough down to release air, and then separate the dough into 12 even pieces; they don't have to be perfect!
Roll each piece into a sphere and place them in a buttered oiled cast-iron skillet or baking pan.
Cover the skillet with a clean kitchen towel and let the dough pieces rise for another 45 minutes, until very fluffy.
Whisk the egg with a little water until smooth. Brush the uncooked rolls with egg wash.
Bake the rolls on the bottom rack of the oven at 350℉ for 25-28 minutes, until golden brown. Rotate the pan halfway through your cook time.
Remove, brush with extra butter, and top with flaky sea salt if preferred. Enjoy!