Cook macaroni according to package directions. Drain, toss with melted butter and 1/2 cup of crumbled feta. Set aside.
Lightly oil a 9 x 13 casserole, sprinkle with another 1/2 cup of feta and half the croutons. Spread the macaroni mixtuer over this and top with remaining croutons.
Beat egg whites until stiff. In a separate bowl beat egg yolks lightly. Fold egg yolks into egg whites. Stir in milk, pour mixture over macaroni.
Sprinkle with remaining feta and bake for 45 minutes or until golden brown.
To Prepare Croutons:.
Cut half a loaf of day old bread into small bits and toss in a skillet over medium-high heat with 2 Tbsp olive oil and 2 Tbsp of butter. Spread on a baking sheet and bake for 30 minutes at 250°F Store, in covered container at room temperature for up to 2 weeks.