First, take a clean, deep pot and place it on the stove.
Add water, milk, granulated sugar, flour, and cornstarch to the pot.
Stir with a whisk to prevent lumps from forming.
Cook the pudding over medium heat, whisking constantly, until it thickens to a rich consistency.
Once the pudding mixture has reached a thick, smooth, and slightly runny consistency, turn off the heat and stir in the vanilla powder mixed with mastic.
Stir the prepared water pudding until it cools slightly.
Next, if the water pudding is to be served by turning the bowls upside down, rinse the glass bowls under water to ensure they release easily, then pour the pudding mixture into them using a ladle.
After the pudding is poured into the bowls, they are placed in the refrigerator and allowed to set.
Once set, the puddings are removed from the refrigerator, garnished as desired, and prepared for serving. Enjoy!