Ensure the unsalted butter is at room temperature and fully softened.
In a mixing bowl, combine the softened butter with the truffle oil and fine sea salt.
Using an electric hand mixer, beat on medium speed for 2–3 minutes until light, fluffy and the truffle oil is fully incorporated.
Taste and adjust seasoning, adding more truffle oil or a pinch of salt if you prefer, then mix again until even.
Spoon the mixture onto a sheet of cling film, shape into a log about 4 cm in diameter and twist the ends to seal (or transfer to a small airtight container).
Chill in the fridge for at least 30 minutes until firm.
Use on toast, steak, pasta, eggs or popcorn. Keep in the fridge for up to 2 weeks or freeze for up to 3 months.