In a large mixing bowl, add glutinous rice flour, cornstarch, and sugar. Gradually whisk in milk until you have a smooth, lump-free batter.

Strain the mixture through a fine sieve to ensure the texture is silky. Cover the bowl with plastic wrap and poke a few holes on top to allow steam circulation.

Prepare a steamer and bring the water to a boil. Place the covered bowl inside and steam for 20 minutes over medium heat without opening the lid.

Once steamed, immediately stir in the unsalted butter while the dough is still hot. Mix until fully combined.

When the dough cools slightly (about 40°C or warm to the touch), knead it with gloved hands for 5–8 minutes until smooth and stretchy.

If using food coloring, knead it in until the color is even. Divide the dough into 30 g portions and keep covered with plastic wrap to prevent drying.

In a cold, grease-free bowl, whip the chilled heavy cream and sugar with an electric hand mixer on medium speed until stiff peaks form. The cream should hold its shape without drooping. Store in the refrigerator until needed.

Lightly dust your surface and rolling pin with cooked glutinous rice flour. Roll out one mochi piece into a circle about 8 cm in diameter — slightly thicker in the middle and thinner on the edges.

Place it into a small bowl mold. Pipe or spoon some whipped cream into the center, add a peeled mandarin, and top with another small spoonful of cream.

Gather the edges toward the center, pinch to seal tightly, and trim any excess dough. Coat the daifuku lightly with cooked glutinous rice flour to prevent sticking.

Place the finished daifuku on a serving plate. For a final touch, you can pipe a small dollop of whipped cream on top and place a small segment of mandarin as a garnish.

Enjoy immediately, or chill in the fridge before serving for a cool, refreshing treat.