Preheat your oven to 200 degrees, pop the 4 metal clips off around the lense, take the bulbs out, whack the light in the oven for 45 seconds - 1 minute, take it out the oven, gently prise off the lense with a flat headed screwdriver making sure you don't crack the glass, then paint the unused parts of the reflector black, wait for it to dry and then put the lense back on, followed by the clips and bulbs..
Did it on my old car and it looked spot on..
