Preheat the oven to 375 degrees F. Grease a 9x13" baking dish with cooking spray.
In a large skillet over medium heat, add the bacon and cook until your preferred doneness.
Remove the bacon from the skillet, leaving the grease in the skillet.
Add the onion and potatoes, cooking until the potatoes have softened, about 10-12 minutes.
Add the kale, and stir to combine. Cook until kale has softened and wilted, about 3-5 minutes.
In a medium bowl, whisk together the eggs, milk, dijon mustard, and salt.
Add the potato/kale mixture, chopped bacon, and shredded cheese to the baking dish.
Top evenly with egg mixture.
Bake in the prepared oven for 35-40 minutes, until middle has cooked through.
Serve and enjoy!