Roast the leg in vegetables as described (see No. 417); an hour and a
half would be sufficient; when done, place a paper frill on the knuckle,
and lay it in your dish; have ready prepared the following sauce: put
the yolks of three eggs in a stewpan, with half a pound of fresh butter,
the juice of half a lemon, a little pepper, salt, and two tablespoonfuls
of tarragon vinegar; place it over a moderate fire, keeping it stirred
with a wooden spoon, and when the butter has melted and begins to
thicken (great care must be taken that the eggs do not curdle, which
they will do if you allow it to get too hot before the butter is melted,
or allow it to boil in the least), add a pint of white sauce (No. 7),
and a little sugar; mix all well together, pass through a tammie into a
clean stewpan, place again over the fire to get hot (but not to boil),
keeping it stirred; add half a gill of cream, and if too thick a little
milk, pour it over the lamb, have ready a few pistachios each cut in
eight lengthwise, sprinkle over, and serve very hot.