Allow Unsalted Butter (125 gram) to soften at room temperature.
Place Sea Urchin (4) in a fine sieve and press through the mesh into a bowl using a rubber spatula.
Place butter and sea urchin paste into the bowl of a food processor.
Mince the Shallot (1 tablespoon).
Zest the Lemon (1).
Add minced shallot, lemon zest, Salt and Pepper (to taste) to the food processor.
Blend the mixture until smooth. Transfer to a bowl and chill in the refrigerator until firm enough to work with, about 1 hour.
Lay the butter out onto a piece of plastic wrap and roll into a log shape about 1½ inch in diameter
Return butter to the refrigerator to chill until solid, or seal tightly and freeze to use later.