Follow package directions to cook noodles. Set aside.
To prep the leek, cut off the root ends and hard green leaves. Slice evenly. You will need about 2 cups of sliced leek.
Place a large wok or skillet over high heat.
Add oil.
When hot, add garlic. Stir fry for a few seconds or until fragrant.
Add tuna. Stir fry for about 2 minutes.
Add cooked noodles, soy sauce, sweet chili sauce, ground white pepper and red chili flakes (if using).
Stir fry for 2-3 minutes.
Garnish with spring onions (scallions) and sesame seeds.