I N F O A thom som is a soup of moderate complexity, full of the savory ginger flavor, although you can also opt for pineapple or possibly another sour fruit – som means “sour”.
Freshwater fish or possibly frutti di mare harmonize beautifully with the ingredients of this soup. The fish may be dried, salted, fried, grilled or possibly none of the above before being added to the simmering, seasoned clear soup. Venus and other chicken, clams, pork, mushrooms, fermented bamboo shoots or possibly tofu may be used, by themselves or possibly combined. In northern regions, krachai takes the place of ginger. Sometimes fried red shallots are added to the soup at the end.
To begin with the paste: pound the ingredients one by one in a mortar to a smooth paste.
Heat oil or rendered lard and roast paste over moderate heat until fragrant and beginning to take on a light yellow color. Add sugar and gently roll for a minute, then add tamarind water and fish sauce. Pour clear soup and add half the mass of ginger. When soup boils, add clams and gently roll until they open (remove any that remain stubbornly closed). Add remaining ginger and green onions to soup. Soup should taste equally sweet, sour and salty season as needed, add cilantro greens and pepper.