I sent a letter and SAE with US Stamps on to the Stage Manager on: 19th December 2011, and today I recieved this signed playbill by both Patti and Mandy.
address I used was:
Stage Manager of ' An Evening with Patti Lupone and Mandy Patinkin',
c/o Ethel Barrymore Theatre,
243. West 47th Street,
New York
NY 10036
USA