Preheat the oven to 350° F.
Whisk the eggs, crème fraiche, rosemary and thyme in a large bowl. Stir in half of the Monterey Jack. Set aside.
Place a 10-inch ovenproof skillet over medium heat. (I prefer a well-seasoned cast iron.)
Add 1 Tbsp. of oil. Once it begins to smoke, add the leeks. Cook the leeks until they begin to soften, and then add the mushrooms. Cook for an additional 5-10 minutes or until they are soft and all the liquid has evaporated.
Stir the mushroom and leek mixture into the egg mixture. Season with salt and pepper.
In the same skillet, heat 2 Tbsp. of oil until it begins to smoke. Immediately add the sweet potatoes and cook for 10-15 minutes or until soft.
Pour egg-leek mixture over the sweet potatoes and cook until the edges begin to set, about 5-8 minutes.
Sprinkle the remaining cheese over the top. Bake 25-30 minutes or until the edges are golden brown and the center is set.