Put the chapati flour into a large bowl and add the salt and the yeast. Use your fingers to mix and blend the dry ingredients. In a separate bowl, combine 2 tablespoons of the melted butter, the yogurt and warm water. In the bowl of an electric mixer fitted with the hook attachment or, alternatively, with your hands, combine all of the ingredients. Knead the dough with the mixer on low speed until it becomes smooth, 8 to 10 minutes. Again, alternatively, knead the dough on a lightly floured flat surface.
Pour the remaining 2 teaspoons of melted butter into a bowl large enough to hold the dough. Coat the sides and bottom of the bowl with the butter and put the dough in the center. Cover the bowl with a kitchen towel and keep it in a warm place. Allow the dough to rise for 1 to 1 1/2 hours.
Preheat the oven to 500 degrees F.
Using a pastry brush, lightly grease 2 baking sheets with some canola oil. Slide the baking sheets into the center of the oven for a few minutes. (Chef's Note: Be careful to not leave the baking sheets in the oven for too long, otherwise you'll risk the oil getting too hot and smoky.)
Gently roll the dough into a 9-inch circle on a lightly floured surface so it is about 1/4 to 1/2-inch thick. Cut the disk into quarters. Roll each quarter to 1/8-inch in thickness and still be able to fit 2 on a baking sheet.
When all the ovals are rolled, brush off any excess flour. Remove the baking sheets from the oven and arrange the naan in a single layer, 2 pieces per pan. Bake until they are light brown and puffy, about 5 minutes. Remove the baking sheets from the oven and transfer the naan to a serving platter lined with kitchen towels to keep them warm.