Mix levain (sourdough starter), milk, and egg well.
Add flour, sugar, and salt, then mix until the batter is smooth.
Heat a pan over medium-low heat and melt butter.
Pour the batter into the pan and cook for about 3–4 minutes.
Flip and cook for an additional 2–3 minutes.
Serve the finished pancakes with butter, maple syrup, or other toppings.