Combine warm water, yeast, and sugar in a large bowl; let sit for five minutes or till bubbly. Add olive oil, yogurt, egg, salt and 2 cups of flour to the yeast mixture. Stir till smooth.
Add enough flour to make a soft dough. Knead a few times on a floured counter until smooth.
Place dough in a greased bowl. Cover and let rise in a warm spot until doubled, 30-60 minutes.
Cut the dough ball into eight equal portions. On a floured work surface, use a rolling pin to roll out each piece into a 6" circle.
Preheat a large skillet to medium heat.
Add a little oil or non-stick spray to the skillet. Cook each circle for 2-3 minutes or until bubbly and golden brown on the bottom. Flip over and cook for another 2-3 minutes.
Brush the top of each naan with melted butter. I added garlic to my butter, but that is optional.