Yes you can make a parallel harness like on this page (second part, "Use 2 parallel-connected battery packs")
http://www.scriptasylum.com/rc_speed/_lipo.html.
I have done the same thing as that (6s1p 4900mah and 3s2p 9800mah) in my truggy with a 1515 1y 2200kv and it works well.
With the 2 plugs coming out of your esc, make one side the same as in the diagram, and for the other side use a plug with a bridge wire (just joins the two plug terminals), so it completes the circuit. You could make it so there's only one plug from the esc, but then you'll need to make a series adapter for when you want to run them is series, so it depends what you want.
Best to charge and balance them together in series even when running in parallel.