Place rice in a bowl and make a shallow indentation in the center. Break the whole egg into the center. Season with 1/2 teaspoon soy sauce, a pinch of salt, a pinch of MSG, 1/2 teaspoon mirin (if using), and a pinch of Hondashi (if using). Stir vigorously with chopsticks to incorporate egg; it should become pale yellow, frothy, and fluffy in texture. Taste and adjust seasonings as necessary. Sprinkle with furikake and nori (if using), make a small indentation in the top, and add the other egg yolk (if using). Serve immediately.