Right now, when you buy a regular size poutine at New York Fries, you can get a second one for $2. To get the discount, you'll need to get a coupon on the Mother's Day Deal tab on their Facebook page (you'll need to "like" the page in order to see the content).
A popup will come up asking you to post the coupon on your wall, but you can click cancel and get to the screen where your coupon is ready to be printed. The coupon is valid today through May 21, and there's a limit of one coupon per customer. You can redeem the coupon at participating New York Fries locations (but it isn't valid at theatres or at the Woodstock highway location).