I read about this on somebody's site while searching for a recipe awhile ago. Sorry I can't remember the author.
1 cup salted butter, room temperature.
1 cup vegetable oil ( don't use olive oil)
Mix in blender until smooth.
Store in fridge.
This works well for those of us who don't want to consume margarine or can't remember to take the butter out of the fridge the night before our morning toast.