Souffle of Spinach And Goat Cheese

Butter a five-cup souffle dish, making sure to butter the rim well.
Place oven rack in lower third of oven and preheat oven to 425 degrees.
Remove spinach stems and wash leaves.
In a large saucepan of boiling salted water cook spinach, uncovered, about three minutes or until very tender.
Drain.
Rinse under cold water and drain again.
Squeeze by handfuls until dry.
Puree in a food processor until finely chopped.
Crumble cheese or cut into pieces and set aside.
In a small, heavy saucepan, melt butter over low heat.
Add flour and cook, whisking constantly, about two minutes, until foaming but not browned.
Remove from heat.
Gradually whisk in the milk, bring to a boil over medium-high heat, whisking, reduce heat to low, continue to cook, still whisking, about two minutes.
Whisk in spinach puree and goat cheese, bring to a simmer.
Season lightly with salt, pepper and nutmeg.
Remove from heat and whisk in the egg yolks, one at a time.
Heat gently until slightly thickened, but do not allow to boil.
Re-season if necessary.
Beat egg whites with cream of tartar until stiff but still supple.
Quickly fold one-quarter of the whites into the warm spinach mixture.
Spoon the mixture into the remaining whites and fold in lightly but quickly.
Transfer mixture to prepared souffle dish and smooth the top.
Bake 20 minutes till puffed and browned.
Souffle should shake slightly in the center when the dish is moved.
Do not overbake.
Serve at once.