Bring the chicken broth to a boil in a medium saucepan; keep warm over low heat.
Heat 1 tablespoon olive oil and 1 tablespoon butter in a medium saucepan over medium heat. Add the leek, season with salt and cook, stirring occasionally, until softened, about 5 minutes. Add the rice, season with salt and cook, stirring occasionally, until the rice is coated, about 1 minute. Add the wine and cook, stirring constantly, until completely absorbed, about 1 minute.
Ladle about 1/2 cup hot chicken broth into the risotto and cook, stirring, until absorbed. Continue to add the broth in about 1/2-cup increments, stirring until absorbed before adding more, until the rice is tender and creamy, about 18 minutes. (If you¿ve used up all the broth and the rice is not yet tender, stir in a little hot water.)
During the last 5 minutes of cooking the risotto, heat a medium nonstick skillet over high heat and add the remaining 1 tablespoon olive oil. Season the scallops with salt and pepper and add to the skillet. Cook, undisturbed, until browned and crisp, 2 to 3 minutes. Flip the scallops and continue to cook until just cooked through, about 1 more minute. Remove to a plate.
Stir the remaining 2 tablespoons butter, the parmesan, lemon juice and all but a pinch of the lemon zest into the risotto until creamy. (Add a splash of water to loosen, if necessary.) Season with salt and stir in the parsley and chives. Divide between bowls and top with the scallops; sprinkle with the remaining lemon zest.