Think of Om’s heavy, decoratively carved wooden door as a portal: On one side is the hubbub of Harvard Square; on the other is what should be a peaceful retreat, with low lighting, a glittery water sculpture, and Buddha statues in every nook. It’s oh-so-hip and has been a surprise hit in Harvard Square. After all, where else can locals find surprising, and often divine, combinations like chef Rachel Klein’s take on surf ’n’ turf: seared tuna with five-spice short-rib dumplings? Klein’s inspirations are ethereal, if a little precious. Take the early-hit tuna tartare: Bruléed with a blowtorch, it’s served with an artful smear of pomegranate molasses, a teaspoon of cubed ginger gelée, and a shot of hibiscus spritzer. The pairings are heavenly, yet so delicately arranged that it’s devilishly hard to get a bite of everything at once.