In a large saucepan, combine the butter & heavy cream over medium heat. When the butter has melted, stir in the spinach, salt, & nutmeg. Stirring occasionally, bring the mixture to a simmer, & cook for 3 minutes.

In a small bowl, blend the cornstarch & water so the cornstarch dissolves. Add to the spinach mixture, & continue stirring until thickened, for about 2 minutes.

Stir in the cheese. Add some pepper, to taste.