In a large mixing bowl, combine 1 1/2 cups flour, yeast, sugar, baking soda, and salt. Add warm water, oil, and yogurt to flour mixture. Blend at low speed until moistened; beat 1 minute at medium speed. Switch to the dough hook and gradually mix in remaining flour to make a smooth dough, add more or less flour as necessary. (I only used 2 1/2 cups flour.) Knead for 5 minutes.
Place dough in lightly oiled bowl and turn to grease top. Cover; let rise until dough doubles, about 45 minutes.
Preheat oven to 400° with a pizza stone on the center rack. (At least 30 minutes before baking naan so your stone gets really hot.)
Punch the dough down, and divide dough in to 6 pieces. Let it rest five minutes covered. Roll out each piece of dough in to a tear drop shape about 8 inches long and 1/4 inch thick.
Cook naan two at a time, use a spray bottle to lightly mist each piece of dough with water and put it wet side down on the pizza stone. Cook for about 2 minutes until the bottom is lightly browned and starting to puff. Spray with additional water and flip the naan over and cook an additional 2 minutes.
Remove from the oven and brush lightly with melted butter.
Wrap naan in aluminum foil to keep them warm until ready to serve.

Naan