To make the sponge: Weigh your flour; or measure it by gently spooning it into a cup, then sweeping off any excess. Mix the sponge ingredients together in a mixing bowl. Cover the bowl and set it aside for 4 hours (or up to about 16 hours), until the mixture is bubbly and has a nice aroma., To make the dough: Add the dough ingredients to the sponge, and mix and knead to make a smooth, soft (but not sticky) dough. Adjust its consistency with additional flour or water, if necessary., Divide the dough into 8 balls (106g each, about 2 1/4", the size of a tennis ball). Let them rest, covered, for a half hour in the refrigerator., Stretch each ball into an oval shape a scant 1/4" thick., To grill the naan: Heat your grill on high; make sure it gets good and hot. Brush one side of the flatbread with oil and lay it, oiled side down, on the grill grate. Close the grill lid (if your grill has a lid). After 1 minute, pick up the bread with a spatula, turn it 45°, and put it back down to cook for another minute; it'll start to puff up a bit. Oil the top side, then turn it over, cover the grill or pan, and cook for 2 minutes to finish. Remove the naan from the heat. Repeat with the remaining pieces of dough., To cook naan on the stovetop: Heat a cast iron pan over medium-high heat. Brush one side of the naan with oil, and lay it into the pan. Cover the cooking bread with a pot lid; start checking after 1 minute; the bottom should be turning golden brown. If not, give it more time. Oil the top side, turn it over, and cook for an additional couple of minutes or so, until brown and cooked all the way through. Remove the naan from the heat. Repeat with the remaining pieces of dough., To serve, brush the naan with melted butter or ghee, and season it with salt and pepper while it's still hot. Stack the breads to keep them soft., Store naan, well-wrapped, on the counter for two days; freeze for longer storage.