Combine the sourdough starter, yogurt, flour, salt, sugar, and oil in a large bowl. Knead until smooth. The dough will be very thick. If your yogurt doesn't contain much whey and it's very thick then the dough might be too dry. Add in a tablespoon or two of water as needed.
Let the dough rest at room temperature for 4-8 hours until bulked out by around 50%.
Optional cold-proof. Cover the dough tightly and transfer to the fridge and let it ferment overnight or up to 36 hours.
On a lightly floured surface, divide the dough into 8 equal pieces and shape into balls.
One at a time, roll a dough ball out into a circle or oval, around 3mm (1/8 inch) thick. Brush the top with a little olive oil.
Heat a skillet on medium-high heat until hot, then cook the naan oil side down for about 1-2 minutes per side until bubbly. Meanwhile, brush the top side with more olive oil. Flip the naan and cook for another 1-2 minutes.
Place the cooked naan in a stack, covered with a clean kitchen towel to trap steam. This helps to keep them soft and warm.
Garlic butter
Melt butter in a pan and add crushed garlic. Cook briefly to remove the raw bite, then stir in chopped parsley. Brush the warm naan with garlic butter and a sprinkle of flaky salt and serve immediately.