Crack the eggs into a large bowl. Whisk eggs along with the milk and salt. Set aside.
In a 10-inch cast iron skillet over medium heat, cook the chopped bacon for about 8 to 10 minutes, stirring constantly. I prefer it to be cooked through but not crispy. Remove the bacon with a slotted spoon once you’ve reached the desired texture, and leave the grease in the pan. Set the bacon aside.
Add the asparagus and leeks to the pan. Cover and cook the vegetables in the bacon grease over medium-low heat for about 5 minutes, until tender. If you're using thin asparagus, you may want to add the leeks first and let them cook for a couple minutes before adding the asparagus.
Return the cooked bacon to the pan and pour the egg mixture on top. Bake for about 15 minutes, or until set.
Sprinkle with chopped chives or other fresh herbs (e.g. parsley) for garnish and serve warm.