In a mixing bowl, whisk together the glutinous rice flour and sugar to combine. Gradually add water, stirring until the mixture is smooth and free of lumps. The dough should have a thick, batter-like consistency.

Transfer the mochi mixture into a steaming dish lined with parchment paper to prevent sticking. Cover tightly and steam over simmering water for about 25 minutes.

Once steamed, carefully remove the dish from the steamer and let the dough cool for 5-10 minutes. Lightly dust a clean surface with cornstarch to prevent sticking.

Once the dough has cooled enough to handle, dust your hands with cornstarch to avoid sticking. Divide the dough into equal pieces, flattening each into a disc. Take a peeled peach, place it in the center, and wrap the dough around the peach, sealing any openings tightly.

Place the wrapped Whole Peach Mochi on a plate dusted with cornstarch to prevent further sticking. Refrigerate the mochi for at least 30 minutes.

After chilling, slice the Whole Peach Mochi in half to reveal the juicy peach inside. Serve immediately.