Grease two 9-inch round pans or one 13 x 9-inch pan with butter and set aside.
Stir water,1 tbsp sugar and yeast together in a small bowl and set aside until frothy, about 10 minutes.
Whisk together flour, remaining 2 tbsp sugar and salt in the bowl of a stand mixer. Add yeast mixture, butter, milk and 2 lightly beaten eggs. With a wooden spoon, stir together to form a ragged dough.
Place bowl on stand mixer fitted with a dough hook. Mix for 7 minutes on medium-low.
Scrape dough into a large, well-oiled bowl; turn to coat. Cover with plastic wrap or a clean, lightly-dampened kitchen towel and allow to rise in a warm area until doubled in size (about 1 hour 15 minutes).
Turn dough onto a lightly floured surface and punch down. Divide into 18 equal portions.
Pinch bottoms and roll gently to form balls.
Place in pan(s), evenly spaced apart, and cover lightly with plastic wrap or kitchen towel. Let rise until doubled in size, about 1 hour. Preheat oven to 375° F.
Beat remaining egg and brush gently over dough balls. Sprinkle with salt, sesame seeds, poppy seeds and/or dehydrated onions, if desired.