Preheat the oven to 425 degrees F. Grease or line a 12 count muffin tin. Set aside.

In a large mixing bowl whisk the flour, sugar, baking powder, baking soda, and salt.

In a small bowl combine the melted butter, sourdough discard, Greek yogurt, egg, and vanilla extract. Whisk well to combine.

Add the wet ingredients to the dry ingredients and fold to combine till just combined. Be careful not to overmix.

Divide the batter between the muffin tins and sprinkle with the large grain sugar (optional).

Place the muffins in the center rack at 425 degrees and bake for 8 minutes. Without opening the oven, decrease the oven temperature to 350 degrees and bake for about 12 minutes longer or till baked through and light brown. Insert a toothpick, it should come out clean if they are done.

Let muffins cool for 10 minutes then remove them to cool on a wire rack.