Herbed Ham and Cheese Baked Eggs

2 Tbsp olive oil

1 sweet onion, thinly sliced (about 1 1/2 cups)

1/2 tsp freshly ground black pepper

1 1/4 tsp kosher salt, divided

3 cloves garlic, finely chopped (1 Tbsp.)

12 large eggs

3/4 cup sour cream

2 tsp Dijon mustard

4 oz Gouda cheese, shredded (1 cup)

1/4 cup chopped fresh flat-leaf parsley, plus more for topping

3 oz Parmesan cheese, finely shredded (about 2/3 cup), divided

8 oz deli smoked ham (8 slices), torn into pieces

1/4 cup finely chopped fresh chives, plus more for topping

 Preheat oven to 350°F with racks in center and upper third positions. Heat oil in a 10-inch cast-iron skillet over medium. Add onion, pepper, and 1/4 teaspoon salt; cook, stirring occasionally, until onion is lightly browned on edges, 6 to 8 minutes. Add garlic; cook, stirring often, until fragrant, about 1 minute.

Meanwhile, whisk eggs, sour cream, mustard, and remaining 1 teaspoon salt in a large bowl until thoroughly combined. Whisk in Gouda, chives, parsley, and 1/3 cup Parmesan.

Pour egg mixture over onion mixture in skillet and scatter ham over top. Cook, stirring gently and scraping along edges of skillet, until eggs are just beginning to set and form creamy curds, 3 to 4 minutes. Sprinkle with the remaining 1/3 cup of Parmesan.

Bake on the center rack until the edges are puffed and center is almost set, about 10 minutes. Transfer skillet to upper rack and increase oven temperature to broil. Broil until lightly browned on top, 2 to 3 minutes. Remove from oven and let cool for 5 minutes. Top with chives and parsley. Serve warm or at room temperature. Serves 8