Cut the scallions in thin slices, separating the white bulb from
tender greens. Heat the butter in a skillet, add the white part
scallions and the mushrooms, and toss and cook over medium heat
Pour in the vermouth and let boil a few seconds, add half the
the crabmeat, and the scallion greens, stirring. When hot, stir
sour cream and/or yogurt, and salt and pepper to taste. Cook just
enough to heat through.
Divide evenly over hot buttered toast,
scatter the remaining tarragon on top.
Recipe from "The LL Bean Book of NEW New England Cookery"