2lbpork belly block(You can increase the meat up to 4 lb/2kg. For 3-4 lb meat, please increase the seasonings by 50%; Japanese grocery stores sell pork belly without the rind, but if there is any, ask the butcher to remove it.)
Gather all the ingredients. My pork belly was from a Korean market and it was pre-sliced into ¼ inches (6 mm). If you buy a block of pork belly, you can freeze the meat for 30-60 minutes and slice with a sharp knife (see this post) or cut into 2" x 2" or 5 cm x 5 cm cubes, which are typical Japanese pork belly (Kakuni) shapes.
We will only use the green parts of the green onions (use the white parts in miso soup to go with this dish). Cut the green parts in half. Peel the ginger and slice it thinly.
Press the “Sauté” button on your Instant Pot (I use a 6 QT Instant Pot) and heat the oil. Cook the pork belly. You can skip this part to cut down the cooking time, but it will render more fat and make the dish tastier.
Pour water just to cover the meat, then add the green onions and sliced ginger. Cover and lock the lid. Make sure the steam release handle points at “sealing” and not “venting”. Press the “Keep Warm/Cancel” button on the Instant Pot to stop cooking. Press the “Manual” button to switch to the pressure cooking mode. Change the cooking time to 35 minutes. If you’re using a stove-top pressure cooker, cook on high heat until high pressure is reached. Then reduce the heat to low to maintain high pressure for about 30 minutes.
When it is finished cooking, the Instant Pot will switch automatically to a “Keep Warm” mode. Slide the steam release handle to the "Venting" position to let out steam until the float valve drops down, OR let the pressure release naturally (takes about 15 mins). Unlock the lid and drain the cooking water and discard the green onion and ginger. Rinse the pork belly under warm water.
Put the pork belly back in the Instant Pot and add ½ cup water, ¼ cup sake, ½ cup mirin, ½ cup soy sauce, and ¼ cup sugar. Mix the seasonings a little bit and add the boiled eggs. Press the “Sauté” button on the Instant Pot and press “Adjust” once to increase the heat. Bring it to simmer to let the alcohol evaporate (no more than a minute). Then press “Keep Warm/Cancel” button to turn off the Sauté mode. Cover and lock the lid. Make sure the steam release handle points at “sealing”. Press "Manual" and set the cooking time to 10 minutes for slices and 20 minutes for 2" x 2" cubes.
When it is finished cooking, the Instant Pot will switch automatically to a “Keep Warm” mode. Slide the steam release handle to the "Venting" position to let out steam until the float valve drops down and unlock the lid. If you have time (this is optional), press the “Sauté” button and simmer on low heat until the liquid in the cooker has reduced by half.
Serve the rice in a (donburi) bowl and pour the sauce on top. Place the pork belly and egg (add blanched green vegetable if you have any). Pour additional sauce over the meat and serve immediately. If you like it a bit spicy, sprinkle shichimi togarashi (Japanese seven spice). Enjoy!
You can keep the leftovers in an airtight container and store in the refrigerator for up to 4 days and in the freezer for a month.