1 small red onion, halved lengthwise and thinly sliced crosswise
In a heatproof bowl, soak the morels in the boiling water until softened, about 20 minutes. Rub them to loosen any grit, then lift them out. Let the soaking liquid stand for 5 minutes so the grit falls to the bottom. Pour off the liquid, leaving any grit behind, and reserve.
In a small saucepan, simmer the morels in the heavy cream over low heat, stirring a few times, until they absorb the cream, about 8 minutes. Season with salt and pepper.
In a small bowl, combine 6 tablespoons of the reserved morel soaking liquid with the ketchup, rice wine vinegar, ginger, garlic and soy sauce. Blend well and season with salt and pepper. Set the dressing aside.
Put the flour, egg mixture and crushed crackers in separate shallow bowIs. Dredge each morel in the flour, shaking off the excess, then dip it in the egg mixture, then coat with crushed crackers. Set aside on a floured platter.
In a medium saucepan, heat 1 inch of vegetable oil until shimmering. Add 4 or 5 morels at a time and fry over moderate heat until golden brown, about 1 minute. Using a slotted spoon, transfer the morels to a plate and keep warm.
In a large bowl, toss the watercress with the onion and the dressing. Scatter the morels on top and serve at once.
The morels can be prepared through Step 2 and refrigerated for up to 1 day. The dressing can be refrigerated for up to 2 days.
By itself, tangy watercress with a soy sauce dressing would be too sharp to be wine-friendly, but the addition of fried morels adds enough fattiness to make a crisp, herbaceous California Sauvignon (or Fumé) Blanc a natural choice.