Use a grater to grind 2 tablespoons of garlic.
Then, use a grater to grind 1 tablespoon of ginger.
After that, add 1 tablespoon of sesame oil into a pot and turn on fire to medium. Add grind garlic, ginger and stir fry them a little bit.
Pour 1.5 cups of soy sauce into the pot.
Next, put 1 & ¾ cups of white sugar, ¼ cup of brown sugar and ¾ teaspoon of black pepper into the pot. Mix it well.
After, let it cook until it's boiling. Then, turn the fire to very low and simmer for 15-20 minutes. (Be careful it may overflow if the fire is too high. Keep stirring it once a while.)
In the meanwhile, in a small container add 4 tablespoons of cornstarch and 3 tablespoons of water. Mix it very well.
Remember to mix the cornstarch very well before pouring into the sauce. Keep stirring the sauce for a minute and wait until it's boiling again. Then, simmering for 5 minutes. (Stir it once a while.) Lastly, add 1 teaspoon of sesame seeds (this is optional) and stir it well.
Let it cool down before putting into a container. When the sauce cools down, it will be thicker.