What's the best way to get to Biarritz by train from Barcelona?

You can check here:
http://www.bahn.com/i/view/USA/en/index.shtml

Via Toulouse and Perpignan (but it takes a long time).

The ones that route through France are twenty hours or so. There's an early morning one and a late afternnon one that go through Irun and Hendaye that only take seven or eight hours.