Overmixing pancake batter develops the gluten in the flour, resulting in tough, flat pancakes instead of light and fluffy ones. Mix just until the ingredients are combined.
Pancake batter relies on a delicate balance to achieve its signature fluffy texture. Flour contains gluten, a protein that forms elastic strands when mixed with liquid. While gluten is desirable in bread, it's the enemy of tender pancakes.
When you overmix pancake batter, you excessively develop the gluten. This creates a network of strong gluten strands that make the pancakes chewy and dense. The batter also loses air, resulting in flat pancakes.
The ideal pancake batter should be slightly lumpy. This indicates that the gluten hasn't been overdeveloped. It's okay to have a few streaks of flour remaining. As long as the wet and dry ingredients are mostly combined, you're good to go. The heat of the griddle will take care of the rest.
Use a whisk for mixing, but switch to a spatula for the final few stirs. The spatula is less efficient at mixing, helping you avoid overmixing. Also, let the batter rest for 5-10 minutes before cooking. This allows the gluten to relax slightly, resulting in even more tender pancakes.