He fen (河粉, literally river noodle — ho fun in Cantonese) are the wide, flat, fresh rice noodles that are one of the most important noodle forms in Cantonese and southern Chinese cooking. Made from a thin batter of rice flour, water, and starch that is steamed in flat sheets and then cut into wide ribbons (2-3cm), fresh he fen is extremely delicate — it must be used the day it is made, as it stiffens and tears within hours of leaving the steamer. The key preparations using he fen: beef ho fun (gan chao niu he, 干炒牛河 — dry-stir-fried beef with ho fun noodles), cheung fun (rice noodle rolls), and various soups.
The rice noodle batter for he fen: 200g rice flour, 50g tapioca starch (for smoothness and slight elasticity), 600ml water, 1 tsp salt, 2 tbsp neutral oil. Mix to a very smooth, thin batter. Rest 30 minutes. Steaming he fen: Oil a flat baking tray or steamer tray. Pour a thin layer of batter (approximately 3mm). Steam over rapidly boiling water for 2-3 minutes until the sheet is set and slightly translucent. Cool briefly. Roll or fold. Cut into strips 2-3cm wide. Gan chao niu he (干炒牛河, dry-fried beef ho fun) — the definitive test of wok technique: Velveted beef slices stir-fried with fresh ho fun, bean sprouts, scallion, dark soy, and light soy at very high heat. The dish must be cooked at maximum wok temperature, with the ho fun sheets tossed and separated without breaking. The noodles must absorb the dark soy colour while developing wok hei. Gan (dry) refers to the absence of added liquid — the dish should have no sauce.
Fuchsia Dunlop, Land of Fish and Rice (2016); Eileen Yin-Fei Lo, Mastering the Art of Chinese Cooking (2009)