Step 1: In a large mixing bowl, combine the flour, milk, and sourdough starter. Mix until no dry streaks remain, cover with plastic wrap, and leave at room temperature for at least 6 hours or refrigerate overnight.
Step 2: The next morning, whisk in the eggs, melted butter, honey, and vanilla. Sprinkle in the baking powder, baking soda, and salt. Stir gently until smooth but avoid overmixing. The batter should be thick but pourable; add a splash of milk if needed.
Step 3: In a hot griddle, melt the butter over medium heat. Add the diced or sliced apples and cook for 3–4 minutes until they begin to soften. Stir in cinnamon, nutmeg (if using), and a pinch of salt. Drizzle in maple syrup and lemon juice. Stir well and cook for another 3–5 minutes until the apples are tender and the sauce is glossy and slightly thickened.
Step 4: Preheat a skillet or griddle to medium heat (around 325°F). Lightly grease the hot pan with butter or oil. Pour ¼ cup of pancake batter per pancake onto the hot surface and cook until bubbles form on top and the edges look set. Flip and cook another 2-3 minutes until golden brown. Transfer cooked pancakes to a parchment-lined baking sheet or cooling rack while you finish the rest.
Step 5: Stack your warm sourdough pancakes high, spoon the maple apple topping generously over the top of the pancake, and serve immediately. Add another drizzle of maple syrup if you love a little more sweetness.