Preheat the oven to 375 degrees Fahrenheit. Whisk the eggs, half and half, salt, and pepper in a mixing bowl until smooth. Place aside.

Melt butter in a 10-inch nonstick pan over medium-low heat. Cook, turning regularly, until the bacon is crispy and the fat has rendered in the skillet. Transfer the bacon to a dish with a slotted spoon. All except 1 tablespoon of bacon grease should be removed.

Turn the heat up to medium and add the leeks. Cook for 4-5 minutes, until the leeks are soft, seasoning with salt and pepper. Pour the whisked eggs into the pan after the leeks are soft. Stir gently to spread the leeks evenly.

Sprinkle the crispy bacon and cheese on top of the frittata. Place the pan in the oven for 16-18 minutes, or until the eggs are puffy and slightly jiggling. Remove from the oven and allow it cool in the skillet for 10 minutes.

Place the frittata on a platter and top with chopped chives before cutting into wedges. Serve right away.