Pour water, brown sugar, and cacao powder into a small saucepan. Simmer on medium heat until brown sugar is dissolved, about 3 minutes. Whisk until all the solids have dissolved.
Turn off the heat and add vanilla extract. Let cool and pour into a mason jar. Store in the fridge.
Chocolate Milk Tea
Pour soy milk, cacao powder, and chocolate chips into a small saucepan. Bring soy milk to a boil. Whisk to get the lumps out. Shut off the heat and add tea bags. Steep for 5 minutes. Remove tea bags.
Chocolate Boba
Bring water to a boil. Add tapioca boba and cook 30 minutes on medium heat, stirring every few minutes. (Cooking time will vary depending on the type of boba you get - check directions on package.)
Turn off the heat. Pour boba through a fine mesh strainer to drain the liquid. Pour boba into a bowl. Pour the chocolate simple syrup mixture over the top. Let marinate 15-20 minutes.
For serving
Scoop chocolate boba into two glasses.
Pour chocolate milk tea over boba.
Notes
Store any leftover cooked boba in chocolate simple syrup for up to 3 days.Use the leftover chocolate simple syrup for coffee, pancakes, or ice cream.