Optionally tie the pork with kitchen twine. Sear the block on all sides in a hot pan until browned.
Put the pork in the pressure cooker inner pot and add the soy sauce, sake, sugar, water, leek greens, and sliced ginger. Cover with a foil drop-lid with a 1 cm hole poked in the center.
Seal the lid and pressure cook for about 20 minutes (roughly 1 hour total including coming up to and releasing pressure).
When the pressure has released, open the lid and flip the pork so both sides soak in the liquid. Let it cool in the braising liquid (ideally until fully chilled).
Slice to your preferred thickness and serve over ramen or rice, warming the slices in a little braising liquid if you like.