THE sight of Kanye West smiling is a rare one – but it seems Kim Kardashian knows how to make his heart sing. The smitten couple looked head-over-heels as they ventured out in New York Sunday night. En route to a performance of Broadway musical Book Of Mormon, Kim was in fits of laughter as she trailed behind her rapper boyfriend. Kanye attempted to play it cooler, but he couldn’t prevent a smile from emerging on his oft-stern face. Reality TV star Kim kept her assets covered up for their theatre date, stepping out in a black frock that drew attention to her curvy hips. Typically, Kanye didn’t dress nearly as smartly – opting for trainers, white jeans, T-shirt and jacket. By the time they arrived at the venue, the hip-hop star’s mug had returned to its normal serious state. Still, at least he proved that he is capable of expressions of contentment. Earlier in the day, Kim flashed a little more flesh in a plunging red blouse, offering onlookers a teasing glimpse of her ample assets. The socialite teamed her low-cut top with beige trousers and cascading centre-parted hair straight out of a shampoo ad. It’s little wonder Kim appears to happy in the company of her famous fella – it’s been reported the Stronger star is gearing up to propose to the brunette once her divorce is finalised. It’s claimed he’s having a ring designed using a ruby ring and earrings that belonged to his late mum Donda. A source said: "Kanye is always showering Kim with gifts but this one is special. "He adores anything belonging to his mum so giving Kim this is poignant. Tongues are wagging in Kanye’s camp that he’s going to use it to propose. "They’re infatuated with one another and openly talk about their future.” Last October, Kim filed for divorce from second hubby Kris Humphries – just 72 days after marrying the basketball ace.  TheSun