Rub the tuna with olive oil and roll in crushed peppercorns and coriander seeds.
Sear the tuna in a hot griddle pan for 2 minutes on each side then keep warm.
Soak the rice noodles in cold water for 5 minutes until softened then drain.
Rub spring onions with oil and griddle in a hot pan for 3 to 4 minutes.
Boil broccoli florets in water for 3 minutes then drain.
Stir-fry broccoli in a wok with oil for 1 minute then add spring onions, sesame oil, coriander, and soy sauce.
Toss the soaked noodles into the wok with the vegetables.
Whisk together the vinaigrette ingredients in a small bowl.
Serve the noodles topped with tuna and drizzled with the vinaigrette.