Microwave butter covered with kitchen towel in glass measuring cup or bowl. Melt for 45 seconds - 1 minute.
Carefully remove hot glass measuring cup from microwave with kitchen mitts.
Add brown sugar and mix well with whisk.
Add ½ cup of heavy cream and mix well with whisk.
Place back in microwave covered for 1 - 2 minutes.
Carefully remove hot glass measuring cup from microwave with kitchen mitts
Add ¼ cup of heavy cream and mix well with whisk
Cool completely and pour into glass mason jar.
Cover and chill in refrigerator overnight.
Next day, remove and mix well. Keep stored and chilled in the refrigerator.