Place the flour in a large mixing bowl or in the bowl of a stand mixer fitted with the dough hook. Add the sugar and salt to one side of the bowl and the yeast to the other. Stir to combine.
Add the yogurt, oil and warm water and stir to form a rough dough. It should be very soft and sticky but if it feels soupy you can add a bit more flour until it is sticky but not runny. If it feels too dry add a drop more water. If it's not sticking to your hands then it is too dry!
Knead for about 5 minutes, it will still be sticky but should become smoother. I knead it by hand in the bowl by pulling the dough upwards then folding it. Be prepared to get a bit messy!
Cover the bowl and set aside to rise in a warm place for about 90 minutes until doubled in size. You can also place the bowl in the fridge to rise for 8-24 hours.
Turn the risen dough out onto a flour dusted surface and dust with more flour as needed to prevent it from sticking. Divide it into 4-8 even pieces, depending on how large you want your naan to be. Loosely cover and leave to rest for 20 minutes.
Meanwhile make the garlic butter by mixing the melted butter and crushed garlic together in a bowl.
Place a cast iron skillet or heavy bottomed frying pan over a medium-high heat.
Take one of the pieces of dough and stretch or roll it out into a rough triangle shape, dusting with flour as needed to prevent it from sticking.
Brush the skillet with a little oil and carefully transfer the triangle to the hot skillet. Brush the dough with some of the garlic butter and cook until it becomes bubbly.
Flip the naan over and cook until browned, about 30 seconds - 1 minute. Transfer to a plate and brush with more of the garlic butter.
Repeat with the rest of the dough balls, brushing the skillet with a little more oil as needed.
The cooked naan breads can be kept warm in a low oven if needed. They are best eaten freshly cooked but will keep in an airtight container for two days.