In a large mixing bowl, whisk together the yogurt, egg, sugar (if using), and vanilla extract until smooth and well combined.
In a separate bowl, sift together the flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, stirring gently until just combined. Be careful not to overmix; the batter should be thick but smooth.
If the batter is too thick, add 1–2 tablespoons of milk at a time until it reaches your desired consistency.