Set oven to 350 degrees F (set oven rack to lowest position).
Spray a 13 x 9-inch glass baking pan with cooking spray then pour the melted butter into the pan.
In a bowl whisk eggs and salt until smooth and well blended.
Gradually whisk in the half and half and milk; pour into the baking pan.
Bake uncovered for 10 minutes.
Remove the pan from the oven then stir the eggs; return to oven and bake another 15-20 minutes or until the eggs are just set (to insure soft fluffy eggs - do not overbake as the eggs will cook more after removing from the oven).
Serve immediately.