You could use a "Butter Bell (pot, crock)." This explains what they are:

http://www.reluctantgourmet.com/butter_crock.htm

http://www.webexhibits.org/butter/crocks.html

Here are some tips for using a butter bell:
http://www.thekitchn.com/thekitchn/good-questions/good-question-do-butter-bells-really-work-014288

Here is Emile Henry's. Click on the different colors to see the pot in that color. It also comes in white, but doesn't show that on this page:
http://www.surlatable.com/product/id/126791.do

Emile Henry Couleurs Butter Pot, White
http://www.pronto.com/Emile-Henry-Couleurs-Butter-Pot-10800097622-CG

Hope that helps.

Joy