Pre heat oven to 400 degrees
Pre cook bacon in skillet , remover and allow to cool on paper towel to drain away grease.
Chop leek (white and green parts) into small mixed pieces and sauté in the warm bacon grease for 6-7 mins. Remove for heat an allow to cool.
In a mixing bowl add eggs with salt, pepper, nutmeg, dijon mustard and Half & Half. Whisk gently for 1-2 minutes, until the mixture is a solid light yellow color.
Crumble bacon into chunks in pie shell and toss with Gruyere cheese only and leeks.
Pour egg mixture of the the top.
Bake for 35 minutes at 400 degrees. Remove from oven and add the Cheddar Cheese to the top for the last 10 minutes of cooking, to avoid burning.
Allow to cool for 10 -15 minutes prior to cutting.