Oil your wok with the vegetable oil. Put on a medium high heat and add the mince. Cook for around 5 minutes, moving around often with a wooden spoon, until caramelised.
Chop your broccoli into inch long chunks. Add to the wok and cook for 2 more minutes.
In the meantime, make your sauce. Put the peanut butter, soy sauce and chilli oil (if using) into a bowl with 100ml boiling water. Stir until combined.
Add the noodles and sauce to the wok. Cook and stir well for another 5 minutes until the noodles are warmed through and the sauce is coating everything. Serve immediately.