In a bowl, combine the water, chicken stock powder, shirodashi, grated garlic, and sesame oil. Stir until the seasonings dissolve completely, then refrigerate until well chilled.

Cook the noodles according to the package directions. Drain well, rinse under cold running water, and chill in ice water. Drain thoroughly.

Divide the chilled noodles between two serving bowls. Pour the cold broth over the noodles and arrange the naruto, ham, bamboo shoots, soft-boiled egg, and green onions on top. Serve immediately.