Prepare the Tapioca: In a large pot, soak the granulated tapioca in hot milk for about 30 minutes, allowing it to soften.
Combine Ingredients: After soaking, stir in the coconut milk, condensed milk, and sugar. Mix thoroughly until all ingredients are well combined.
Cook the Mixture: Put the pot on low heat and continuously stir the mixture as it thickens. This process should take about 10-15 minutes.
Add Coconut: Once thickened, remove from heat and gently fold in the grated coconut for an added texture and flavor punch.
Set the Cake: Pour the mixture into a greased baking dish, smoothing the surface. Allow it to cool at room temperature before refrigerating it until fully set (about 3 hours).
Serve: Once set, slice the cake generously and drizzle each piece with additional dulce de leche to taste.