Soak the uncooked tapioca pearls in water for at least 4 hours or overnight, then drain using a fine mesh strainer.

In a large mixing bowl, whisk together the all-purpose flour, milk powder, granulated sugar, and salt until evenly distributed.

Cut in the chilled unsalted butter until the mixture resembles coarse crumbs. Add the egg and vanilla extract, mixing gently until a cohesive dough forms.

Preheat your oven to 350°F (175°C). Roll out the dough on a floured surface until it’s about 1/4 inch thick. Fit the rolled dough into your baking dish and bake for 15-20 minutes until lightly golden.

In a medium saucepan over medium heat, whisk together the milk, soaked tapioca pearls, eggs, granulated sugar, cornstarch, and vanilla extract until thickened and bubbly, about 8-10 minutes.

Once thickened, pour the custard over the pre-baked crust, smoothing the top as necessary.

Return to the oven and bake for an additional 25-30 minutes until the custard is set and the top is golden.

Allow the pudding to cool at room temperature for at least 30 minutes, then slice and serve warm or chilled.