In cast iron skillet, heat oil over medium high heat. Add diced onions and cook for about 3-4 minutes, stirring occasionally.
If oven-proof skillet not available, vegetables can be cooked and then placed in greased pie plate or other baking dish.
3
Add sliced mushrooms and cook until tender and browned, about 8-10 minutes. Add garlic and chopped kale. Season with salt and pepper. Cook until kale has wilted down, about 3 minutes, stirring often.
4
While vegetables are cooking, whisk eggs and milk in a medium bowl. Pour egg mixture over the vegetables in the skillet. Sprinkle the cheese over the top.
5
Bake until set and lightly golden brown on the top, 20 to 25 minutes.