Place 3 cups of dashi into a medium saucepan over moderate heat and bring to a boil. Set one cup of dashi aside.
Once the dashi is boiling, reduce the heat to medium-low, and let it simmer for 5 minutes.
In the meantime, add 3 TBSP of miso paste to the cup of dashi you set aside. Stir until the miso paste has broken down and blended with the water.
Remove the saucepan from the heat, and add the miso mixture to the dashi. You'll immediately see those gorgeous miso clouds (and you'll probably get very excited)!
Add the cubed tofu.