French Onion Casserole

Cooking spray

3 T. olive oil

2 large sweet onions, thinly sliced (about 7 cups)

1-1/2 t. kosher salt, divided

Water, if needed

2 t. apple cider vinegar

2-1/2 c. heavy cream

2 c. unsalted vegetable stock

1 16-oz. package penne rigate or ziti pasta

1-1/2 T. Worcestershire sauce

1/8 t. ground nutmeg

1 medium clove garlic, grated

12 oz. aged Gruyere cheese, shredded, divided

4 oz. sharp white Cheddar cheese, shredded, divided

1 T. fresh thyme

Preheat oven to 350 degrees with 1 rack in center and 1 rack 6" from heat. Lightly coat a 13 x 9" broiler-safe baking dish with cooking spray.

Heat oil in a large skillet over medium-high heat. Add onions and 1/2 t. salt; cook, stirring occasionally, until onions begin to soften, about 5 minutes. Reduce heat to medium; cook, stirring occasionally, until onions are deep golden brown and jammy, 15-18 minutes. Add water 1/4 c. at a time if onions start to burn. Remove from heat and stir in vinegar.

Meanwhile, add cream and stock to a medium saucepan. Bring to a simmer over medium-high heat. Add pasta and simmer, stirring occasionally, until just al dente, 8-10 minutes. Stir in Worcestershire sauce, nutmeg, garlic, and remaining 1 t. salt. Remove from heat. Add most of  Gruyere cheese and half of cheddar cheese, a handful at a time, stirring until melted between each handful.

Stir half of caramelized onions into pasta mixture. Transfer to prepared baking dish and top with remaining caramelized onions. Sprinkle with remaining cheeses. 

Bake on center rack until bubbly, about 20 minutes. Transfer to top rack and increase oven temperature to broil. Broil until cheese is golden brown, about 3 minutes. Remove from oven and sprinkle with thyme.

Let cool for 10 minutes before serving.    

Serves 8.

Adapted from Real Simple magazine, March 2022, p. 94.