Separate bok choy leaves from stems. Slice stems into 6 vertical pieces and halve horizontally. Cut leaves into bite-sized pieces. Mince garlic and halve chili pepper, removing seeds.

Boil water in a pot, add salt (not listed in ingredients) and spaghetti. Cook 1 minute less than package instructions. Reserve 2 tbsp of pasta water.

Heat sesame oil, garlic, and chili pepper in a frying pan over low heat until fragrant. Add bok choy stems and dried whitebait, stir-frying over medium heat until softened.