1.) Preheat oven to 375 degrees F.
2.) In a large skillet, brown sausage and break it into crumbles. Toss in potatoes and cook until coated with oil. Stir in kale and cook until wilted. Season with salt and pepper and take off the heat.
3.) In medium bowl, lightly beat eggs. Season with salt and pepper. Whisk in milk and cheese. Set aside.
4.) Spray 6 small (8 ounce) mason jars with cooking spray. Divide the sausage mixture evenly between the jars. Top each jar with eggs, making sure to leave at least an inch of free space at the top of the jar. Place jars on a baking sheet covered in parchment (the eggs might bubble over a little while cooking.
5.) Bake at 375 degrees F for 25 to 30 minutes, or until eggs are set and top is golden brown. Let eggs rest for 5 minutes before serving. Serve warm or room temperature.*