Bloom the yeast: in a bowl, combine the warm water, yeast, and sugar. Stir and let sit until foamy.
Combine the wet ingredients: whisk in the olive oil, yogurt, and egg until combined.
Make the dough: add the freshly milled flour and salt. Mix until just combined. Let the dough rest for 10 to 15 minutes to allow the freshly milled flour to absorb the moisture.
Knead the dough: sprinkle your counter with all-purpose flour. Knead the dough for 3 to 4 minutes on the counter, sprinkling the dough and your hands with all-purpose flour as needed until it comes together and becomes smooth and elastic.
Let the dough rise: return the dough to your bowl, cover, and let rise for about 40 minutes, until doubled in size.
Shape the naan: generously flour your work surface and hands. The dough will be sticky, so add all-purpose flour as needed to make it easier to handle. Divide into 8 equal pieces.
Roll out: roll each piece into a roughly 6-inch circle, about 1/2 inch thick.
Cook: heat a cast iron skillet over high heat. Place one naan in the hot skillet. It should begin bubbling as it cooks. Cook for about 2 minutes per side, until puffed and browned in spots.
Finish: brush each naan with butter while warm. Serve immediately.