Making standard awase dashi requires roughly 20 minutes from cold water to strained stock. The process demands visual attentiveness rather than high heat. The golden dashi stock ratio generally calls for 20 grams of dried kombu and 20 to 30 grams of katsuobushi bonito flakes per 1,000 milliliters of cold water.
Begin by wiping the dried kombu strip gently with a damp paper towel. Never wash off the white powdery substance clinging to the surface; that powder is naturally dried mannitol, a sweet sugar alcohol that forms during curing and deepens the broth. Place the kelp in cold filtered water and set the pot over low heat. Watch the bottom of the vessel closely. Over the course of 10 to 12 minutes, the stiff kelp will soften, turning dark green and swelling to three times its dried thickness.
Keep a close eye on the simmering temperature. Tiny, pinhead-sized bubbles should emerge along the edges of the pot around 60°C, 65°C. Remove the kombu immediately before the water comes to a rolling boil. If the kelp boils, bitter polyphenols and slimy alginic acid bleed into the stock, turning it viscous and muddy. Once the kelp is out, bring the water to roughly 85°C, 90°C, take the pot off the burner, and scatter the shaved bonito flakes across the liquid. They will dance on the surface tension for a brief second before absorbing water and sinking slowly to the bottom. Let them infuse undisturbed for 2 to 3 minutes, then pour the broth through a fine-mesh sieve lined with cheesecloth or unbleached paper towels. Never squeeze or press the wet flakes; doing so forces sour, cloudy fats into what should be a crystal-clear, amber broth.
