Using a scale, measure out your tallow and oil into a small pot
Over medium-low heat, gently melt until tallow is just about melted, take off the heat.
If its too hot to hold a finger in, let cool until you can hold a finger in for a few seconds.
Add essential oils, stir well.
Let cool either in the pot or transfer to the bowl of your stand mixer. You want it to cool so it isn't liquid, but not return to a fully solid state.
Once cool, whip like buttercream! It goes very quickly so keep watch on it.
Scoop into desired containers and label.