Whisk the egg and baking powder in a large bowl. Add the milk, sugar, 1 teaspoon salt and 1 cup water. Stir until smooth. Add 4 1/2 cups of flour and mix slowly. Add additional flour if necessary. Knead the dough until smooth, 5 to 10 minutes.
Preheat a lightly oiled grill on high, about 500 degrees F.
Divide the dough into 3 to 4 tennis-ball-sized pieces of dough. Roll the balls out into a thin circle and place on the preheated grill. Cook, turning once, until puffed and lightly browned, less than 1 minute. Continue the process until all of the naan is cooked, then brush with melted butter.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.