Each time I bake a yeast based coffee cake, the center collapses as it cools. I've tried the recipe several times and this has happened all but one time. I beat the batter at high speed, as directed; I prepare the whole recipe as directed. It comes out beautifully, but again as it cools the center collapses and is doughy. The toothpick comes out clean at the end of baking time. What am I doing wrong?
There could be several reasons. It might be the amount of moisture in your flour - that varies depending on the humidity. Even though you're following the recipe, the amount of moisture your flour is holding could cause the batter to be too loose and therefore not able to hold the structure after baking. You could try adding a few tablespoons of flour to the batter, or a little less liquid.
Another factor might be your oven temperature. Have you tested it with an oven thermometer? Many ovens are slightly off. Some yeast bread/cake recipes recommend a higher initial temperature, and then the oven is turned down for the remainder of the baking time. The purpose is to get that initial inflation from the yeast reacting to the heat. By heating up faster, the dough rises better and the structure is formed to hold that rise after the bread/cake has cooled.
Another issue might be your pan size. I assume you're using the size recommended in the recipe. If it's too small for the amount of batter, the batter might be too dense near the middle to fully cook. It can pass the toothpick test, but still not be "done" enough to maintain the structure once it's cooled. Yeast bread loaves are ideally baked to an internal temperature of 200 degrees F. They can look done at a lower temperature, and they can pass the toothpick test, but they are often gummy in the middle unless they're baked to that temperature. I'm not sure what the optimal temperature would be for your coffee cake, but I would try baking it longer. You can cover the top with a sheet of aluminum foil near the end of the baking time to protect it from over-browning.
Try these tips and don't give up!