Add stock, simmer for 1 minute, then add noodles and cook for 45 seconds, flipping halfway, then separate.
Add coconut milk, peanut butter, vinegar; stir to dissolve. Toss in spinach, cook 30 seconds until wilted. Serve topped with coriander, peanuts, and chilli if desired.
Notes
Make sure to keep the sauce saucy and serve immediately for best flavor.