Preheat the oven to 425 degrees F.

Chop up all the vegetables and herbs.

In a large bowl, with a fork beat together the eggs for about a minute, add the milk, 1/2 tsp of salt, the fresh herbs and sprinkle with some freshly ground black pepper. Add half the cheese and mix it together. Reserve the remaining half for later. Set aside.

On a 9X13 inch cast iron or oven-safe skillet heat the butter and olive oil together over a medium high heat. Add the leeks. Cook for about 2 minutes. Add the asparagus and mushrooms. Sprinkle them with a 1/4 Tsp of salt. Cook stirring constantly for another 2 minutes.

Arrange the mixture in an even layer across the skillet.

Whisk eggs one more time just for a few seconds and add the egg mixture to the skillet. Sprinkle remaining 1/2 cup of cheese all over it, and arrange the tomato slices around it.

Transfer the pan to the bottom of the oven and bake until you can see the middle just barely set for about 12 to 14 minutes. For a browned crisp top, set frittata under the broiler 12 minutes after baking and broil until frittata is puffed and begins to turn golden in color for about one minute. Watch this really close as the frittata can turn dark brown in a matter of seconds. Do not walk away from it!

Once the frittata is done, let it rest for 5 minutes before slicing it. Serve immediately.

Leftover frittata will keep well stored in a glass covered container, refrigerated for up to 3 days.

Enjoy!