Place the milk in a bowl and set aside. You do not want it fresh from the refrigerator when you mix the ingredients or it will be too cold. Gently melt the butter in a saucepan over medium-low heat or in the microwave at 50% power (stir every 15 seconds until melted) and then let it cool completely at room temperature. Combine the cooled butter with the milk and mix with a hand mixer until well blended. Use immediately or chill and then remix with hand mixer. Use in place of one cup heavy cream.