I've spent a long time searching before asking so forgive me if this is an obvious question:

What's the best way to plan a route through mountainous terrain? EG: from Lausanne to somewhere in Northern Italy?

Obviously I can't simply climb high and fly direct so how do I plot a route given a FL or altitude or height that gets me through the various routes that exist without actually knowing what those routes are?

Say for example I was happy to fly at 10000ft with a lateral clearance of 2 miles to obstacles and a vertical clearance of 500ft.

Thanks in advance