The Nuomi Chang in some Chinese cultures use blood as a binding agent, similar to Korean ice cream. China has a wide variety of sausages, from black pudding from Hunan to red sausages from Harbin, near Siberia, and even camel sausages from Xinjiang in the far west. You may not find them in most supermarkets, but it's worth looking for a local supplier of Chinese ingredients and searching for a package or two. Horsemeat sausages (xián mcháng or xūn mcháng) from Xinjiang are heavily smoked and bring with them a cuisine previously unknown in China, including sourdough bread, Russian kvass drink, and smoked and cured oriental sausages. Taiwan also produces a similar form of sausage, though they are rarely dried in the manner of Cantonese sausages.
The confusion arises from different Chinese dialects; in the Cantonese dialect (the southern provinces) the sausage is known as Lap Cheong, while in the Mandarin dialect (the northern provinces) it is known as La Chang. This variant of Chinese sausage is known as xiangchang () in Mandarin Chinese, which literally translates to 'aromatic sausage'. Monosodium glutamate (MSG): Chinese people often add monosodium glutamate (a flavor enhancer) to meat and sausages. I remember making a plate of sausages and rice when I took classes decades ago and I would like to replicate it. Because Chinese sausages are generally filled into small diameter casings (~25 mm), the drying process is relatively short and the drying temperature can fluctuate within a wide range, but must be kept below 50°C (122°F).
Sugar is added as food for lactic acid bacteria in fast-fermented sausages to increase acidity (drop in pH). Sausages made in the Chinese province of Sichuan should be hotter than similar sausages made in different regions. In the late 1990s I was living in Huaihua (huai huà), in the west of Hunan province (- hú nán), in south-central China, and discovered that the locals were making blood sausage. Your sausages may be Vietnamese rather than Chinese, but they're possibly made in the Chinese (Cantonese) style. The relatively high drying temperature results in a short drying process due to the small diameter of the sausages, which does not provide favorable conditions for healing and flavor-producing bacteria, such as micrococcus and staphylococcus, to react with meat and develop flavors.
As with other countries, there is no universally followed sausage recipe; each region of China develops its own variation, though the name remains the same. Since traditionally made Chinese dried sausages develop a pleasant and shiny appearance, they are referred to as La Sausages.