Add walnuts into a small bowl and add water to cover. Add rice and sticky rice into a small bowl, and add water to cover. Allow the walnuts, rice, and sticky rice to soak overnight. Peel walnuts following soaking.
Right before making the smoothie, completely drain peanut and rice.
Add walnuts, peanuts, rice, sticky rice and 1 cup of water into a blender or food processor. Blend until the texture of the liquid turns silky, about 2 minutes. Transfer the mixture to a medium sized pot.
Add 1 cup water and the milk into the pot. Heat the pot over medium heat and stir constantly until the mixture reaches a boil. Turn to medium heat and keep stirring constantly (like cooking risotto, you need to stir constantly in case the mixture gets burn on the bottom of the pot), until the grains and nuts are cooked through, about 20 minutes. Add more milk if the mixture becomes too dry.
Add sugar and taste. The texture of the drink should be thin and creamy, thicker than milk but thinner than your average smoothie. You can adjust the sweetness and thickness according to your preference, by adding more sugar and/or milk, or by boiling down the drink.
Garnish with grated peanuts and black sesame seeds. Serve warm or cold.
The drink will stay in fridge for around 2 days.