Preheat the oven to 375ºF. In a large bowl, whisk together eggs and milk. Set aside.
In a 10 inch, non-stick, oven-safe skillet, heat 1 tablespoon olive oil over medium heat. Add the vidalia onion and cook for 2 minutes, stirring frequently. Add the asparagus and continue to cook, stirring often, for another 5-6 minutes. Add the scallions and kale and cook, stirring, for 1 minute or until the kale begins to wilt. Add the egg mixture and stir quickly to incorporate. Sprinkle the cheese over the top and season with salt and pepper.
Transfer the skillet to the hot oven and let cook 20-25 minutes or until set and just beginning to brown. Remove from the oven and allow to rest for a few minutes before cutting into 6-8 slices.
While the frittata is cooking, heat the remaining 1 tablespoon of olive oil in a medium skillet over medium heat. Add the tomatoes and garlic and cook, shaking or stirring the pan often, until the tomatoes begin to burst, about 10 minutes. Add the balsamic vinegar and allow to cook, stirring often, until the tomatoes become coated in the syrupy juice.
Serve slices of frittata topped with burst tomatoes and sprinkled with dried parsley if desired.