The European Union continues to mull several different plans to continue trade with Iran without fearing US sanctions. Germany, France, and Britain are advocating an idea that would involve establishing a clearing house to handle all the trade.
The big stumbling block with EU companies continuing to trade with Iran is financing. US threats to punish companies involved in such trade have scared away a lot of banks, despite EU assurances that they will protect companies.
This clearing house would aim to avoid banks, and money changing hands across borders, entirely. One European company could pay the clearing house for imported Iranian oil, and the clearing house would give that money to another EU company providing goods or services to Iran.
While the US theoretically wants to sanction all trade with Iran, particularly oil imports, they have limited options to punish a European company whose business is to buy Iranian oil, or European industrial firms with projects inside Iran.