Traditionally, oyakodon recipe starts with simmering chicken in dashi broth. Once the broth simmers, add sliced chicken thighs, onion slices, and scallions. There’s no oil in Oyako Donburi. The eggs are lightly whisked but the egg white and yolk are still distinct. Saute the onion slices to add flavor base to the broth.
Combine dashi, mirin and shoyu in a large skillet and bring to boil; add chicken, mushrooms and onion. When cooked, reduce heat and sprinkle green onions. In a small bowl, beat eggs slightly and pour over cooked ingredients evenly. Cook until egg is coddled. In the meantime, fill donburi bowl 2/3 full with hot rice.
Donburi means - rice bowl. So the dish literally means chicken and eggs in a bowl, served over hot rice. The photo is not my own but to give you an idea of what is looks like. It's a bit much as you cannot see the hot rice below. IMPORTANT NOTE: The bamboo shoot is optional as quite a few people find the aroma and taste objectionable.