Found this tiny malatang place on Sharp Street East called Xiao La Jia. The owner is from Chengdu and makes it properly spicy — Not the watered-down Hong Kong version.

You pick your ingredients from the fridge (vegetables HK$8 per 100g, meat HK$15-25), they weigh it and cook it in the numbing spicy broth. Get the extra spicy level if you can handle real heat. Most Hong Kong people can't finish it.

Open until 11pm, cash only. Fair warning — You will sweat.