> To listen, go to bostonglobe.com/soundtrack. I would be perfectly content eating every meal at the cluster of Japanese restaurants and shops in Cambridge’s Porter Square: pastries for breakfast, udon soup with tofu and tempura for lunch, a spicy tuna roll and edamame for dinner. Maybe a bubble tea for an afternoon treat. It’s all under one roof, in a former Sears building on Massachusetts Avenue long known as the Porter Square Exchange. Although the owner, Lesley University, forced out a beloved Japanese market to make more room for a bookstore, the building’s first floor remains a haven for Boston-area Nipponophiles. The noodle shops throb with life. But all that noise and activity falls away behind the sushi bar. On a recent Friday afternoon, I slipped behind the counter at I (Heart) Sushi to listen to the sushi-making. The work was quick, precise, graceful, the resulting craft at once simple and intricate. And it was all done with a quiet intensity: the chef spreading sticky rice onto seaweed wrappers, carefully laying pieces of fresh fish on top, slicing through avocado with a knife, and piling heaps of pickled ginger and wasabi on the plate.