In a medium saucepan, combine 1 cup of kokuto sugar with 1/2 cup of water. Heat over medium-high until it begins to boil, then reduce to a simmer for about 5-7 minutes, stirring occasionally until the sugar dissolves and thickens. Remove from heat and let cool.

Bring 3 cups of water to a rolling boil in a kettle or pot. Add 4 teaspoons of loose-leaf Assam tea and steep for 3-5 minutes. Then strain out the tea leaves.

Pour the warm brewed Assam tea into a large mixing glass or bowl. Slowly add in 1 cup of whole milk while stirring gently. Pour in the cooled brown sugar syrup based on desired sweetness, mixing until the syrup is fully integrated.

To serve, pour over ice for a chilled drink or enjoy warm. Top with tapioca pearls if desired.