To start, you will need a good strong dashi. The addition of a little reduced dashi broth brings that hit of amino acids you get from konbu and dried, smoked bonito. I like to reduce 1 cup of dashi by half, then add this to the shoyu and sugar. I do not like to heat the marinade, but, I have made a few adjustments to allow for this.
2 cups Shoyu (I used Yamasa Brewed, but, Tamari is great too)
1/2 cup reduced dashi
1/2 cup agave syrup (adjust for sweetness desired)
1/4 cup sake
1 tablespoon grated ginger
1 tablespoon grated garlic
1/2 teaspoon togarashi sesame oil
A few of the marinade ingredients
Mix all above ingredients at room temperature. Do not heat. I believe that heating at this stage muddies the flavors of the elements in the marinade. I check for taste at this point, I want the marinade to be moderately sweet, but, showing lots of complexity. Too much sugar at this point overpowers the other elements. The overall sensation should be a taste that starts off salty, moved to aromatic and snappy, finishing with sweet and heat.
A note about the chicken I use. I strongly prefer the use of quality poultry for this dish. I buy field raised air-chilled chickens for this use, and I avoid the large packer products. I feel that the air-chilled chickens take the marinade better. I place the chicken in a vessel suitable for marinading the meat overnight. This can be zip closure bags or it can be a glass or plastinc container, best if it seals liquid tight though. I like to let the chicken marinade overnight. At least 8 hours, if you must rush it. I will flip and turn the chicken to make sure the marinade is moving around the meat for good coverage.
Chicken Thighs await
A good alternate, one I learned when I did large cooks for the church bazaars that we used to do, is to actually pack the chicken in rock salt, coarse rock salt that works to pull the liquid out of the meat, then you can put it in the marinade for just a couple of hours. This is better and far more efficient, when you are cooking 300-500 chicken dinners. The rock salt will not flavor the chicken, it just pulls moisture and sets up the process of the chicken pulling the marinade into the meat.
Anyway, once it is marinaded, place the chicken in a pan, and place it in a 400F oven (or smoker/kettle/wood burning oven) and let it run for 45 minutes. Do not crowd the chicken. I happen to prefer cooking the chickens in a pan, as opposed to on a rack, as I feel it gives me a moister product. Meanwhile, prepare another batch of the marinade, but, triple the agave syrup, or use honey instead. This forms your glaze. I like to heat this batch to around 180F and let it sit at that temperature for 5 minutes or so. It combines into a glaze. This is brushed onto the chicken about 15 minutes, and again at 5 minutes before the chicken is pulled. It gives it an almost lacquered look.
That is not photoshopped, those were really that shiny and they were not sticky at all. And yes, perhaps I got distracted and was a little tad late pulling them from the heat. The chicken was cooled and packed, the grease and drippings were drained into the 'mother dashi' as nothing was to be wasted. For Osechi, the chicken is normally eaten at room temperature, so it is important that the flavor be balanced for eating at a colder temperature, the marinade I use has plenty of depth and complexity, there is the characteristic sweetness on the skin while the chicken still shines through. It is nothing like any store bought candy chicken sauce.