Fu Pei Kuen (Fried Tofu Skin Rolls)

Variations

• Finished in sauce, as in the photograph: the fried rolls plated and covered in a stock-and- oyster-sauce gravy thickened with cornflour, with spring onion on top. Crispness traded for a wrapper that has drunk the sauce, and common in dim sum houses.
• Sin juk kuen (鮮竹捲): the same film used the other way round. Rolled in dried tofu skin and steamed in a bamboo basket, so the film takes water back and turns very soft; bamboo shoot is the usual filling. The last tip below is about that difference (steaming).
• Vegetarian: tofu, carrot, shiitake and bean sprouts instead of the pork and prawn. The wrapper is soy too, so the ingredients overlap — which makes drying the filling matter more, not less.
• Other fillings: chicken, fish and beef are all used. ko.wikipedia says the same: the filling varies and only the outer skin is always tofu skin.
• What it shares a table with: har gow, siu mai and cheung fun. Four wrappers made of four different things.

Tips

• This wrapper is neither starch nor gluten. Cha gio sorts fried wrappers into two materials: what separates it from a wheat spring roll is that "the wrapper is starch rather than gluten". Har gow holds down the starch end — "on heating there is no protein to set white and opaque — only starch gelatinising, which goes clear". The premise the two share and neither states is that a wrapper is rolled out of a dough. Tofu skin is soy protein, it is not gluten, and it was never rolled out of anything.
• The film is made by evaporation, not by setting. Douhua sets out the two ways soy protein is stood up: "Acid gives you lumps; a salt gives you a gel.". Tofu skin uses neither. Soy milk held just under the boil in a shallow tray loses water from its surface, and the protein and fat left behind there concentrate and knit into a single sheet. The same page writes that "Soy protein has to unfold before a coagulant can attach to it." — here there is no coagulant to attach, and the unfolding is the entire mechanism.
• Which is why each sheet lifted off leaves the milk weaker. The first sheet is the thickest and the fattiest; later ones come thinner and take longer to form. That is what graded tofu skin is about, and thin sheets are simply doubled up.
• Dried tofu skin is limbered, not soaked. Cha gio says of rice paper "Wet it, do not soak it.", and this arrives at the same instruction by a different route. A starch film that takes up water goes gluey; a protein film that takes up water goes slippery and tears along the grain of the sheet. Ten minutes between damp cloths is safe; a bowl of water splits it before you have rolled anything.
• Water in the filling costs more here than in cha gio. That page's "Half the job is getting water out of the filling." holds unchanged, with one extra reason. A starch wrapper gelatinises in the oil into a rigid shell that can resist the steam inside; tofu skin has no starch to set. A wet filling softens the film from within before the oil can dry it.
• One fry, at a lower temperature. Cha gio says "150°C to cook the filling, five minutes' rest, then 185°C to blister.", and what that second pass is for is bursting a starch film into bubbles. A protein film has nothing to blister. What it does instead is go straight to Maillard, protein meeting a little sugar (browning and the Maillard reaction), so the window between gold and bitter brown is short. 160-170C, once, is the whole of it (deep frying).
• Steaming uses the same film in reverse. Frying drives the last water out of it until it snaps like glass; steaming puts water back into a dried sheet until it is tender. One material, two opposite textures, and very little in between — tofu skin warmed halfway is simply tough.