Preheat oven to broil setting and position rack about 6 inches from the top.
Melt butter in skillet. Add leeks and season with salt pepper. Cook, stirring occasionally, until softened, 4-5 minutes.
2 tbsp butter, unsalted
¼ tsp salt
¼ tsp black pepper
Wash and slice mushrooms. Peel and mince garlic.
1 lb white mushrooms
2 cloves garlic
Add mushrooms and garlic to skillet and cook, stirring frequently, until softened, 4-5 minutes.
Wash and dry parsley. Shave leaves off the stems; discard the stems and mince the leaves.
1 small bunch Italian (flat-leaf) parsley
In a medium bowl, whisk together eggs, water, ¾ of the parsley (save the rest for garnishing), salt, and pepper.
12 eggs
4 tbsp water
½ tsp salt
¼ tsp black pepper
Crumble goat cheese and stir about ½ into egg mixture (save the rest for sprinkling overtop).
1 (4 oz) log goat cheese
Spread out leeks and mushrooms evenly in the skillet. Pour in egg mixture. As eggs set around the edge of the skillet, gently lift cooked portions with a spatula to allow uncooked egg to flow underneath. Cook until bottom and sides are firm but the top is still runny, 5-7 minutes.
Sprinkle with remaining goat cheese. Place skillet in the oven until the top is set and lightly browned, 2-3 minutes.
To serve, cut frittata into wedges, place on a plate, and garnish with remaining parsley. Enjoy!