Combine warm water, sugar, and yeast in the bowl of an electric mixer fitted with a dough hook. Let stand five minutes, until bubbly. Add remaining ingredients, leaving the salt for last. Mix for five minutes on medium-high speed. Place dough in a greased bowl, turning it over so that the entire surface of the dough is greased. Cover and let rise for about one hour, until double in size.

Meanwhile, heat olive oil in a large pan. Sauté onions on medium heat until transparent and just beginning to brown. Set aside and cool.

Lightly grease 12 compartments of a muffin pan and set aside. Preheat oven to 350 degrees Fahrenheit.

Cut dough into 12 even pieces and roll each piece into a circle. Place a tablespoon of onions into the center of each circle. Sprinkle with poppy seeds and close dough by joining the outer edges together and pinching them closed, almost creating a sack for the onions. Turn upside down and place seam-side down into lightly greased muffin pans. (Alternatively, you can create rolls by rolling out each piece into a rope between your palms and then flattening the rope with a rolling pin. Spoon some onions along the whole length of the dough and roll it up like a cinnamon bun. Slice into one-inch pieces and place them in lightly greased muffin pans.) Cover and let rise 45 to 60 minutes.

Brush with egg wash and sprinkle additional poppy seeds or fried onions, if desired. Bake for 25 to 30 minutes. Remove from muffin pan and cool on wire rack.

Combine dill, butter, and salt (if butter is unsalted) in a bowl and mix with the back of a spoon.