In a large bowl, dissolve yeast in warm water. Let stand about 10 minutes, 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 1 hour, until the dough has doubled in volume.
Punch down dough, and knead in garlic. Pinch off small handfuls of dough about the size of a golf ball. Roll into balls, and place on a tray. Cover with a towel, and allow to rise until doubled in size, about 30 minutes.
During the second rising, preheat grill to high heat (I use a griddle).
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 browned, another 2 to 4 minutes.
Remove from grill, and continue the process until all the naan has been prepared.