Cooking over medium heat will ensure that your butter will cook evenly. Finish the last few moments of the browning process off the heat! As soon as the butter is just about the perfect color for your recipe (3-4 minutes after foaming stops), remove it from the heat source immediately and keep whisking. The heat from the pan will complete the browning. Pour into your heat-resistant glass or ceramic bowl (no plastic!) to stop the process and cool.