You can find fresh and frozen paneer, a cheese used in Indian cooking, at Indian markets. Feta cheese or goat cheese are good substitutes.
In a glass measuring cup, combine the yeast, sugar, and water and let sit for 10 minutes. In the meantime, mix the flour, baking soda, and baking powder in a large bowl.
Whisk together the yeast mixture, yogurt, and milk, and stir into the dry ingredients. Knead with your hands until the dough forms a smooth, soft ball, about 2 minutes. Place the dough in an oiled bowl and cover with plastic wrap. Leave at room temperature until doubled in size, about 2 hours.
Remove the dough from the bowl and turn onto a well-floured surface. Knead it briefly and divide the dough into 12 equal portions. Roll it into 1/4-inch thick ovals, approximately 6 inches wide.
Heat a cast-iron skillet over moderately high heat. Brush with melted butter and place in skillet. Cook for about one minute, until dough puffs up. Flip, cover pan, and cook for one more minute. Remove from pan and brush both sides with butter and sprinkle with salt. Place on a baking sheet and top with crumbled paneer. Broil in oven for 2 minutes, until cheese just begins to melt and naan turns golden brown.
What size cast iron skillet? Four cups of flour will make a pretty big naan.