Place a glass bowl on top of a pan partially filled with water over medium heat. Put the butter in a glass bowl, and cook in the kettle until it's completely melted.
Carefully remove the bowl (and melted butter) from the heat source. Add oil, and mix to combine the ingredients.
At this point, the oil mixture should cool down (with the bowl). If not, let it rest for a few minutes. Then place the mixture in the refrigerator and allow it to harden.
After the mixture is a little hard (not solid like a rock), take the bowl from the refrigerator. Add vanilla oil.
If You use cocoa butter in body butter, then stir the mixture with a fork until it looks like body lotion.
Spoon body butter into jar with lid. Place the lid in the jar. Store body butter at room temperature (outside the sun).