2 cups soy sauce
3/4 cup (100 grams) brown sugar
1/2 cup (115 grams) rock sugar (or granulated sugar)
1 big thumb ginger, coarsely chopped
6 green onions
3 bay leaves
1 star anise pod
1 small cinnamon stick
1/2 teaspoon fennel seeds
1 Cao Guo (or black cardamon)
Add soy sauce into a small sauce pan. Heat over medium high heat until boiling.
Add the rest of the ingredients. Stir and cook until the sugar completely dissolves and the liquid starts to simmer again.
Turn to medium low heat. Simmer until the liquid is reduced to about two-thirds of the original volume, and the soy sauce is thick enough to coat the back of a spoon. Check on the pan every 15 minutes. It could take anywhere from 30 minutes to more than one hour, depending on the heat and the pan you use. Remove the pan from the stove.
Line a sieve over an airtight glass container or a jar and pour in the soy sauce. Discard all the solid ingredients.
Let the soy sauce cool completely. It is ready to use. Or you can store it covered in the fridge for a year.