In a large bowl, mix the yogurt and warm water. Stir in the yeast and allow the yeast to bloom for 5 minutes or until bubbly.
Mix in the softened butter, egg, salt, and garlic powder.
Mix in the flour one cup at a time until well incorporated.
Knead dough on a heavily floured surface until mostly smooth. It is a very wet dough, hand kneading may require additional flour. (or use a dough hook and knead in a kitchenaid mixer)
Place finished dough in a well oiled bowl, turning to coat in oil. Cover with a kitchen towel. Place dough in a warm oven on the proofing setting. (if your oven does not have this setting, set your oven to 100 degrees and turn off after a minute before placing your dough inside) Allow dough to rise until doubled, about 30 minutes when using a warmed oven.
Shape dough into 8 equal balls. Place balls on parchment paper or silicone baking liners on the baking sheet. Press down on buns to give them a slightly flattened top. Allow to rise while oven preheats for about 30 minutes.
Preheat oven at 350 degrees. Mix egg white and 2 Tbsp water and brush over the buns.
Bake at 350 degrees 25 minutes or until tops are golden brown.
(optional) Mix garlic powder and butter, brush onto buns.
Allow buns to cool, slice and enjoy!