Begin by preheating the oven to 350°F. Butter the inside of a 9" x 13" baking dish and set aside.
In a mixing bowl, whisk together the wet ingredients (milk, butter, eggs and vanilla).
In a separate mixing bowl, whisk together the dry ingredients (glutinous rice flour, sugar and baking powder).
Begin combining the the wet ingredients with the dry by adding ½ of the wet mixture to the dry ingredients, stirring well until you reach a smooth but thick consistency. Continue adding the wet mixture a cup at a time, working out any lumps before adding more. Repeat until all the wet ingredients are mixed in and you end up with a smooth and silky batter.
Pour the batter into the buttered baking dish.
Drop red bean paste into the batter ½ a teaspoon at a time, randomly but evenly. The trick is to keep it small enough so it doesn't sink to the bottom but large enough so that it floats in the middle of the batter.
Bake at 350°F for 1 hour and 10 minutes. The top should develop a beautiful golden crust. Let it cool completely before cutting and serving.