Preheat oven to 375 degrees Fahrenheit.

Heat 3 tablespoons olive oil in a large cast iron skillet over medium heat. Add leeks and sauté until translucent, about 3 minutes. Add the asparagus and mushrooms and season with ½ teaspoon of kosher salt and ¼ teaspoon of ground black pepper.

Cook the vegetables for 5 to 7 minutes, stirring occasionally, until the vegetables soften and the liquid that is released from the mushrooms begins to evaporate. Stir in greens and cook until just wilted. Remove from heat and set aside to cool slightly.

Roughly tear or chop the croissants into small, bite-sized pieces. You want them small enough to not feel like heavy bites but large enough to soak up the custard well. Add the croissant pieces to a large mixing bowl.

Add the sautéed vegetable mixture to the croissant pieces and toss together to combine.

In a separate medium mixing bowl, whisk together the eggs, egg whites, heavy cream, dash of hot sauce, and a pinch of kosher salt and ground black pepper. Pour the custard over the vegetables and breading. Stir to combine everything tog ether.

Pour the strata mixture into the prepared baking dish. Alternatively, evenly distribute the strata into individual, greased ramekins.

Bake strata for 45 to 50 minutes until golden brown and the custard is set in the center. Remove from oven to cool slightly for about 5 minutes before serving.