In a small saucepan over low heat, warm the milk to around 110 degrees F to make the sourdough starter. Transfer to a medium bowl, top with the yeast, and let stand for 5 minutes or until frothy. Until smooth, whisk in the apple cider, brown sugar, butter, and 1 cup of flour. Overnight, let the covered object stand at room temperature.
Make the pancakes the following morning by combining the sourdough starter with 1/2 cup flour, an egg, baking soda, and an apple. In a cast-iron griddle or nonstick skillet, melt 1 tablespoon of butter over medium heat and stir to coat. For each pancake, pour roughly 1/4 cup batter onto the griddle. About 3 minutes after the edges start to set and the tops start to bubble, flip the pancakes over and cook for another 1 to 2 minutes, or until golden and thoroughly done. Repeat the process with the remaining batter, including extra butter as necessary. If using, top with syrup and add pecans as a garnish.