Cobblers, first made when the pilgrims settled America, allowed early settlers to pick native fruits and prepare a meal over an open fire. These deep-dish fruit pies are a truly American invention. The perfect cobbler has a gooey fruit center encrusted with a sweet breaded top layer. A runny cobbler usually means that the fruit used in the dish was extra juicy. You can correct the runny cobbler by adding a thickening agent. Make sure you fix the filling before you spoon over the topping.
Remove the dish from the oven.
Drain off excess juice by pouring it out of the pan. Don't remove all of the juice or the cobbler will end up too dry.
Add cornstarch into the remaining juice until it begins to thicken. Start with 1/2 teaspoon of cornstarch for a family-sized cobbler, and work from there. Put the dish back in the oven. The secret to getting the cobbler to thicken lies in keeping it hot. The heat will activate the cornstarch and thicken the remaining juices.
Check the cobbler in about 10 minutes to see if it has thickened. If it hasn't, drain off more juice and add more starch. Repeat this process until you achieve the desired results.
Cook the fruit on a stovetop before baking it in the oven. It's better that the juices thicken before you start baking the dessert.