Prepare the Brown Sugar Syrup: Bring ½ cup of water to a boil in a small saucepan. Stir in ½ cup of dark brown sugar until dissolved. Simmer for 2-3 minutes, then cool.
Cook the Tapioca Pearls: Boil 4 cups of water, add 1 cup of tapioca pearls, and cook for 15 minutes. Drain and soak in brown sugar syrup for 5 minutes.
Froth the Milk Mixture: Combine milk, cream, and vanilla extract. Froth for about 2 minutes until smooth and foamy.
Assemble Your Bubble Coffee: Add 3 tablespoons of tapioca pearls to each glass, fill with ice, pour in espresso, and top with frothed milk.
