Your waffle batter is too thick
THE RESULT: Raw in the middle.
THE FIX: Compared to muffins, waffles have a higher liquid-to-dry ingredient ratio. When this ratio gets out of whack and the dry ingredients outweigh the liquid, the result is a doughy or undercooked center. To make sure your waffles get golden-brown (or even almost crispy, depending on how you like them), shoot for a batter that is still slightly thick but pourable and that spreads easily on the waffle iron. If after following the recipe, your batter still seems too thick, add additional milk by tablespoons until the batter reaches the desired consistency. Keep the cooked waffles warm by putting them on a metal baking pan or oven-safe platter in an oven preheated to 200°.