In the bowl of a stand mixer, stir together the warm milk, yeast, and sugar. Let it sit for 5 minutes until the yeast starts to dissolve. Add the sourdough discard, yogurt, olive oil, and salt. Mix to combine. Add the flour a little at a time, mixing on low speed until the dough pulls away from the sides of the bowl. The dough should be soft and tacky but not overly sticky. Kneed for about 8-10 minutes until the dough comes together in a smooth and elastic. After 5 minutes if the dough still seems very sticky, add flour 1 teaspoon at a time.
Transfer the dough to a lightly oiled bowl, cover with plastic wrap or a kitchen towel, and let it rise in a warm place until doubled in size, about 1 hour.
Turn the dough out onto a lightly floured surface and divide it into 8 equal pieces. Roll each one into a tight ball and let them rest, covered, for 20 - 30 minutes.
On a floured surface, using a rolling pin, roll each dough ball into a small circle about 6 - 7 inches wide. You can also gently stretch them by hand for a more rustic look.
Heat a cast iron skillet or frying pan over medium-high heat. Once hot, lightly oil and place one piece of naan in the pan and cook for 30-60 seconds, until bubbles form. Flip and cook another 30-60 seconds on the other side until golden and puffed in spots. Repeat with remaining dough.
Brush the warm naan with melted butter and sprinkle with sea salt or fresh herbs if desired. Serve right away or keep warm wrapped in a clean kitchen towel.