In a large bowl, dissolve yeast in warm water, until frothy.
Stir in sugar, milk, egg, salt, and enough flour to make a soft dough.
Knead for 6 to 8 minutes on a lightly floured surface, or until smooth.
Place dough in a well oiled bowl, cover with a damp cloth, and set aside to rise. Let it rise until the dough has doubled in volume around 30 mins.
Pinch off small amounts of dough to make 10 pieces. Roll into balls, and allow to rise again.
While the dough is rising, preheat grill to high.
At grill side, roll one ball of dough out into a thin circle. Lightly oil grill. Place dough on grill, and cook for 2 to 3 minutes, or until puffy and lightly browned. Brush uncooked side with butter, and turn over.
Brush cooked side with butter, and cook until done, another 2 to 4 minutes.
Remove from grill, and continue cooking until all the naan has been prepared.