Pour 250ml of Spiced Rum into a mason jar. Add 60ml of melted butter to mason jar. Seal mason jar tight and vigorously shake for 10 seconds. Let the mix sit at room temperature for 30 minutes.
Within those 30 minutes, shake the jar two more times. After the 30 minutes, place mix into the freezer for 2 hours.
Once the butter has solidified, strain the mix through a coffee filter or paper towel. Store in a clean jar and keep refrigerated.