Pre-heat your broiler or toaster oven to 350 degrees.
Detach mussels from the shell and replace back. Arrange them in the same way on the baking pan. Set aside as you prepare the sauce.
To prepare the sauce, first drop a pinch of the Hon Dashi pellets in a medium bowl and dissolve completely with the half and half.
Then add the Kewpie mayo. Combine the mixture with a spoon until smooth. Add the Sriracha or chili sauce and fully incorporate it into the sauce.
Do a taste test here. If you would like the sauce to be hotter, add a little more Sriracha or chili sauce. If you want it to be milder, add a few squirts of Kewpie mayo. If you think you've added too much mayo, you can thin the mixture slightly with a few drops of half and half.
The consistency of the sauce should be like pancake batter or a softened milk shake.
Once you've reached this stage, add the roe and stir slowly to distribute it evenly into the sauce. Spoon the sauce over each mussel. Put just enough to cover the meat completely.
Place the mussels under the broiler or toaster oven to cook.
Check frequently and rotate the pan occasionally to even out the browning. Cook until the sauce bubbles and gets golden brown with a few dark spots forming. The total cooking time should not exceed 15 minutes.
Serve immediately, squeeze some lemon juice on each as you are eating them. ENJOY!