Banh chung (square glutinous rice cake) and banh day (round glutinous rice cake) are the most traditional cakes in Vietnamese food culture. Banh chung and banh day is said to be first made by Lang Lieu prince thousands year ago during the Hung's dynasty. The prince later became the country's king for inventing such a meaningful cake which symbolized people's perception of sky and ground during their time: the sky is round (symbolized by banh day) and the ground is square (symbolized by banh chung).
Makes 5 (6-inch) cakes – plenty to share with friends and family
5 1/2 cups glutinous rice
1 1/2 cups split yellow mung beans
2 pounds fresh or frozen banana leaves
1 large yellow onion, thinly sliced
1 teaspoon salt
2 tablespoons peanut oil
wooden or metal mold (optional)
Do following steps:
Place the rice in a large bowl, cover with water, and let soak overnight. Place the mung beans in a separate bowl, cover with water, and let soak overnight. If using frozen banana leaves, defrost them in the refrigerator overnight. The next day, drain both the rice and mung beans.
Place the mung beans in a pot with just enough water to cover. Bring to a boil over medium heat, then reduce to a simmer and cook, stirring occasionally, until mashable, about 20-30 minutes. Mash into a paste with a potato masher or spoon.
Meanwhile, heat the peanut oil in a heavy skillet over medium heat and cook the onions until caramelized, about 30-40 minutes.
Add the onions and salt to the mung beans and stir to combine. Spread the mung beans out on a large platter or baking sheet and let cool completely.
Wipe the banana leaves clean with a damp cloth and spread them out to dry. (A laundry drying rack works well; you can also use the backs of chairs.) If the banana leaves are particularly long, you can trim them.
To assemble, lay out two sheets of partially overlapping banana leaves, place a third leaf on top (perpendicular to the first two sheets), and a fourth leaf on top of that (perpendicular to the third sheet). (If using a mold, place it on your work surface first, then line it with the banana leaves in this manner.) Place about a cup of rice in the center of the leaves and spread out to cover a 6-inch square area (or to fill the mold). Take about a cup of mung beans and, using your hands, pat it into a slightly smaller square and place it on top of the rice. Then take another cup or so of rice and pack it over the top and sides. Starting with the innermost banana leaf, fold the leaves in one at a time, forming a square. Wrap it tightly like a present so that the contents don't shift or spill during cooking, and tie tightly with twine.
Bring a large stockpot of water to a boil. Add the cakes and make sure they stay submerged (a colander or heavy steamer basket can help keep them under water). If your pot isn't large enough, you may need to use more than one. Simmer until the cakes feel plump and the rice is congealed, about 6 hours. Keep an eye on the pot and add more hot water as necessary to keeps the cakes covered.
Place the cakes in a colander to drain and cool completely.
To serve, remove the wrapping and cut into wedges or slices. An easy way to cut the sticky cake is to use a thread or dental floss. Bánh chưng are often eaten with pickled onions or root vegetables, or dipped in sugar for a sweet treat. They can also be sliced, pan fried until golden, and served with sugar.