Cravings are sometimes your body's way of telling you that it needs more of a certain vitamin or mineral. Butter cravings translate into needing more healthy fats or needing salt, or both.
Salt cravings could mean you have a mineral deficiency, particularly calcium. The best calcium-containing foods are dark green leafy vegetables. Your body could also be lacking in potassium (found in avocados and bananas) and iron (found in spinach and seeds).
Salt cravings can also mean you’re stressed, as stress depletes your body of trace minerals--the type that are found in sea salt. Start using sea salt instead of iodized table salt. Just a dash of sea salt a day can help replenish minerals and curb cravings for salt.
Table salt comes from salt mines and goes through extensive processing that strips it of many minerals. In contrast, sea salt comes from evaporated sea water. The specific elements of sea salt vary slightly depending on the geographic area of origin, but its mineral profile contains as many as 75 minerals and trace elements.
You may also find the information at this link helpful:http://www.fitday.com/fitness-articles/nutrition/healthy-eating/understanding-cravings-why-people-crave-salty-foods.html#b