Swiping a finger around a brownie batter bowl is a delight for both cooks and kids. However, having a runny batter that easily drips off your finger is not a good sign -- an overly watery brownie batter means that you will end up with flat brownies that require longer cooking times and risk becoming hard and inedible. You can add flour or chill your brownie batter in the refrigerator to help thicken it.
Chill butter before adding it to the rest of the wet ingredients in the recipe. It will soften as it is added. However, it will not melt and cause the batter to become too runny.
Place the batter in the refrigerator if the batter is runny. You can remove the batter when it reaches the desired consistency, but for best results, leave the batter in the refrigerator overnight.
Add flour, 1 tbsp at a time, to the batter. Continuously stir the batter slowly to incorporate it. Do not add more than 4 tbsp flour or your brownies will be too tough and dry.
Continue adding flour until the batter is thickened to the consistency you desire.