Frittata with Gruyere, Leeks and Chard

1 bunch Swiss chard, though stems discarded

 2 T. unsalted butter

 1 medium leek, white and tender green parts thinly sliced

 1 t. salt, or to taste

 6 lg. eggs

 4 oz. gruyere cheese, grated (approx. 1/4 cup)

Freshly ground pepper to taste

Preheat oven to 425. Wash chard in cold water several times. Drain & transfer to a pot. Cover & cook over high heat for 1-2 min. or until wilted & bright green. Drain & run under cold water until chilled. Squeeze dry &chop. Heat butter in heavy saute pan. Add leek and salt. Cook 5-7 min. until softened; regulate the heat to prevent browning. Remove from heat. Whisk eggs briefly in mixing bowl. Add chard, leek and cheese. Season w/plenty of black pepper & add salt if desired. Butter a 9-in. pie plate or cast-iron skillet. Pour in egg mixture and smooth the surface with a spatula. Bake 35-40 min. or until puffed and golden brown. A knife inserted will come out clean when it's done.