Heat the vegetable oil in a frying pan over a medium heat, then gently fry the chilli, garlic cloves and fresh ginger, peeled and sliced into matchsticks, until crisp. Remove and set aside. Fry the spring onions in the same pan until golden, then remove and set aside.
Bring a pan of water to the boil and cook the green beans for 2 minutes, then add the noodle nests and cook for a further 1-2 minutes until al dente. Drain both and refresh in cold water.
Mix the toasted sesame oil, soy sauce and lime juice in a large bowl. Toss through the noodles and green beans with the cherry tomatoes and the spring onions.
Put the sesame seeds on a plate and press the tuna steaks on top to coat all over. Heat a glug of olive oil in a frying pan over a high heat and cook the steaks for 1 minute on each side. Slice and serve with the noodle salad and crispy aromatics.