01 -
Dish up while it's still piping hot.
02 -
Top the onions with a generous sprinkle of Gruyère cheese. Slide the casserole under the broiler until the cheese is gooey, bubbling, and golden.
03 -
Give a 9x13x3-inch baking pan a coat of cooking spray. Pour in the rice mixture and spread it out. Pile the caramelized onions over everything.
04 -
Take the lid off, mix in heavy cream and the chicken pieces, and warm the whole thing just until it's hot.
05 -
Pour in the chicken broth. Let it start to simmer, drop the heat low, put a cover on, and leave it for 15 minutes.
06 -
Pop the rest of the butter and olive oil in with the cooked mushrooms. Once runny, add the rice and toast for 5 minutes so it gets a bit of color. Throw in the spinach and stir until it just droops, about a minute.
07 -
In another pot or pan on medium-high, toss in mushrooms dry and cook until nicely browned, about 5–10 minutes.
08 -
Crank up the heat to medium. Toss in the garlic and stir for a minute. Sprinkle in salt, pepper, tarragon, and thyme. Let that go for another minute. Remove from heat to pour in the brandy or wine, put it back, then cook off the liquid for about 5 minutes. Mix in Worcestershire. Put onions aside.
09 -
In a big, high-sided skillet on medium-low, melt 2 tablespoons butter with 2 tablespoons olive oil. Toss in the onion slices. Let them be for 15 minutes, stir and keep going 15 more. See if they're brown enough—if not, keep at it 10–15 more minutes, stirring now and then, until they're deeply caramelized.