1. Place butter in medium mixing bowl and with an electric mixer (fitted with a paddle) or wooden spoon, beat until light and fluffy. Scrape down the sides.
2. Beat in the pomegranate syrup or molasses, Clementine zest and sugar, scraping sides of the bowl as needed to incorporate all ingredients. Stir in nuts if desired.
3. Scrape butter into a small bowl, crock or butter mold and cover tightly; or shape into a long roll on grease-proof paper (plastic, wax or parchment) for storing and slicing as needed.
*To make pomegranate syrup, boil 16 oz. of pomegranate juice in a heavy saucepan over medium-low heat until reduced to 1/4 c. You can also use pomegranate molasses - available from many specialty grocers or at ethnicgrocer.com.
**Any orange or mandarin variety may be substituted for Clementines.