Ensure unsalted butter is fully softened at room temperature.
In a mixing bowl, combine softened butter, 1.5 tablespoons of good quality truffle oil, and fine sea salt.
Beat on medium speed for 2–3 minutes until mixture is light and fluffy and truffle oil is evenly distributed.
Taste and adjust: add remaining truffle oil or a pinch more salt if desired, then mix again until uniform.
Spoon mixture onto parchment paper or plastic wrap and roll into a 1.5-inch log; twist ends to seal (or transfer to an airtight container).
Refrigerate for at least 30 minutes until firm.
Use on bread, steak, pasta, eggs, or popcorn. Store in refrigerator up to 2 weeks or freeze up to 3 months.