fine sea salt and freshly ground white pepper to taste
1 bag pre-washed spinach (10 oz.), wilted, squeezed as dry as possible and finely chopped
4 egg yolks
7 egg whites
Recipe
In a heavy saucepan, melt butter, whisk in flour and cook 3 minutes. Add milk, whisking until smooth and thickened. Remove from the heat and stir in the mustard, cheese, spinach and egg yolks. Stir until the cheese is melted, returning the pan to low heat if necessary. Season to taste with salt and pepper. Transfer to a large mixing bowl and cool to room temperature.
Make sure your mixer is super clean. Whisk the egg whites at medium-low speed to soft peaks (they should droop). Do not over beat the egg whites or the souffle will come out dry.
Carefully fold the whisked egg whites into the base, one third at a time. Spoon mixture into a buttered 1-1/2 quart souffle mold. Bake for 30-35 minutes (or 12 - 15 minutes for small individual servings) in a preheated 375F oven. Serve immediately.