Simple. Get India & Pakistan to use all of their nukes ON EACH OTHER; no more nukes, no problem. The only problem is getting the war started without leaving your fingerprints; THAT'S the creative part.
Other than that, I can't think of a way to get EITHER country to voluntarily disarm.
My oponion, with the use of nukes, both the countries will consider these weapons as legit warfighting tools. Using nukes does not destroy the capabilities, nor the technical know how.
They will just rebuilt it. Ofcourse, there is a huge question if India and Pakistan will be allowed to rebuilt it.