Cut the onion in half, and cut each half into ½-inch (1.3 cm) wedges.
Peel the carrot and cut it into 1-inch (2.5 cm) pieces. Here, I use a Japanese cutting technique called "rangiri," where we cut the carrot diagonally while rotating it a quarter turn between cuts. This helps to create more surface area so it will cook faster and absorb more flavor.
Cut each potato into quarters.
Remove the sharp edges of the potatoes with a knife to create smooth corners. Then, soak the potatoes in water to remove the starch. Tip: We call this Japanese cutting technique "mentori." This prevents the potatoes from breaking into pieces. If the potatoes have sharp edges, they are likely to bump into each other and break while simmering.
Remove the strings from the snow peas.
Bring a small pot of water to a boil and add a pinch of salt. Add the snow peas.
Blanch them in the boiling water for 1 minute and take them out. Keep the water boiling.
Drain the shirataki noodles from the package and cut them roughly in half. Blanch the noodles in the pot of boiling water for 1 minute to remove any odor.
Drain well and set aside. Cut the thinly-sliced beef in half or thirds (depending on the size) so that the pieces are about 3 inches (7.6 cm) wide.
To Cook the Nikujaga
Preheat a large pot or Dutch oven (I used a 4-QT Staub cocotte) on medium heat. Then, add the oil and sauté the onion wedges.
When the onion wedges are coated with oil, add the meat and cook until no longer pink.
Add the potatoes and coat them well with the cooking liquid. Tip: This coating will help keep the potatoes from breaking.
Add the carrot pieces and shirataki noodles and mix everything together.
Add the dashi, making sure there's enough liquid to almost cover the ingredients (it doesn't have to fully cover the ingredients). If there's not enough liquid, add water.
Cover with a lid and continue to cook. Once boiling, skim the scum and foam from the surface with a fine-mesh skimmer.
Simmer on low heat for 12-14 minutes, or until a skewer pierces a potato easily. Tip: The otoshibuta holds the ingredients in place and is necessary to maintain the shape of the vegetables. They bump into each other and break easily when they are loose. Do not mix the ingredients while cooking; the otoshibuta will help distribute the cooking liquid and its flavors.
Turn off the heat and remove the otoshibuta. Ideally, let it stand (uncovered) for 30-60 minutes before serving. The flavors will soak into the ingredients while cooling down.
When you are ready to serve the Nikujaga, add the blanched snow peas to the pot and cover to reheat on medium heat. When simmering, reduce the heat and let it simmer for a few minutes. Tip: Add the snow peas right before serving to keep their bright color.
Turn off the heat and serve the Nikujaga with some cooking liquid in a large serving bowl or individual bowls.
You can keep the leftovers in an airtight container or in the pot and store in the refrigerator for up to 3-4 days. Nikujaga tastes even better on the second day! To freeze, remove the potatoes as their texture changes when frozen. You can keep it in the freezer for up to a month.