Heat the butter in a saucepan
over medium heat. Add the flour and cook, whisking, for 1 minute. Whisk
in the wine
and cook until slightly reduced, 1 minute. Whisk in the stock and simmer until thickened. Season with salt and pepper. Add the peas, heavy cream and pimientos and return to a low simmer
. Add the tarragon, mustard and a few grates of nutmeg, then stir in the chicken.
Toast the bread, then liberally butter
and cut corner to corner. Ladle the creamed chicken over the toast points and serve.
Cook's Note: The creamed chicken can be covered and refrigerated for a make-ahead meal. Reheat over medium heat, partially covered.