This is the version of ozōni that I grew up eating, and is common to the Kanto region in the east of Japan (especially the Greater Tokyo Area). It is plainer than other regional versions, but because it’s easy to prepare, you can eat it on a daily basis together with osechi.
For the soup:
Water — 400 ml
Dried konbu seaweed — 1 10 cm piece
Katsuobushi (bonito flakes) — ½ cup (1 small handful)
Light soy sauce — 1 tsp
To add to the soup:
Boneless skinless chicken thigh meat — 60 g
Salt — ½ tsp
Komatsuna greens or spinach — 1 small bunch (about 150 g)
Large fresh shiitake mushroom — 1
Small yuzu citrus — 1
Square mochi cakes (kirimochi) — 4
Make the soup: Prepare the dashi stock by steeping the konbu in the water for 20 minutes, then bringing up to a boil. Add the bonito flakes and turn off the heat immediately. Let stand for a few minutes, then strain the liquid through a fine mesh sieve. Add the soy sauce to the clear dashi stock that remains and set it aside.
Cut the chicken into small pieces and sprinkle with the salt. Wash the greens well and cut into pieces. Slice the mushroom. Cut a piece of peel off the yuzu, and slice very thinly. (My mother used to do all of this in advance and keep the ingredients ready to go in the refrigerator.)
When you’re ready to serve the ozōni, cook the mochi cakes on a mochi-ami grill or in a toaster oven until puffed and slightly browned on the surface, about 5 to 10 minutes. Heat enough water to cover the chicken pieces in a separate pan, and poach them quickly, 1-2 minutes, then drain. Heat up the dashi stock, and add the greens and mushroom. Cook for 1-2 minutes, then add the mochi pieces and simmer for another 1-2 minutes. Add the chicken pieces. Serve piping hot in small bowls garnished with the yuzu peel.