Liquid component: Selzer water (non-sweetened, of course, 1 cup), Vodka (1 cup) and whole egg (one) mixed together.
Dry component: Cake flour (1 cup) and potato starch (1/4 cup). The original recipe calls for AP (all purpose) flour instead of cake flour.
Actually, my dry ingredients were proportionally much less for two crabs and 4 asparaguses. In addition I used only a portion of the liquid mixture to attain the desired consistency of the batter.
The result was a good nice light crust but we were not sure this was any better than my regular batter with or without eggs. Soft shell crab may not be ideal to test the tempura crust because the shell gets crispy even if you don't use tempura batter. We will try again with a more appropriate food medium to assess the crust. In any case, we love soft shell crab tempura and we have to make it at least once in the season.
Talking about the season, the iris were in full bloom in our garden. We were surprised when this pure white one appeared among all its purple cousins. My wife arranged it using a Japanese-style base with "kenzan" 剣山.