Mix all stir fry sauce ingredients in a bowl and set aside.
Boil udon noodles according to package instructions, drain and set aside.
Heat oil in a large wok or pan over high heat. Stir fry all seafood for 2-3 minutes until just cooked. Remove and set aside.
In the same pan, stir fry onions, garlic, carrot, and chili for 2-3 minutes until fragrant.
Add cooked noodles and sauce to the pan, tossing well to combine.
Return seafood to the pan and toss everything together for 1 minute.
Garnish with spring onions and sesame seeds before serving.