Yield: Serves 6 to 8 | Prep Time: 30 minutes | Cook Time: 55 minutes
When people ask what is my favorite thing to cook, I usually say it’s something that lets me stand over the stove and stir, but then allows me to leave it behind and socialize. This dish is a good example of just that. I love the act of sautéing the onions and garlic, watching the butter melt, and patiently waiting as the onions decide to brown. At just the right time, when my guests arrive and I want to step away from the stove, this casserole is ready to be poured into a pan and baked. It’s a sit-by-the-fire, read-a-book, and snuggle-up kind of casserole, one that I hope you enjoy as much as I do.
INGREDIENTS
2 tablespoons unsalted butter
3 large yellow onions, thinly sliced
¼ teaspoon sugar
1¼ cups chicken broth
1½ cups beef broth
1 teaspoon chopped fresh thyme
1 teaspoon Dijon mustard
½ teaspoon kosher salt
½ teaspoon freshly ground black pepper
1 baguette, sliced ½ inch thick (24 slices)
2 cups shredded Gruyère cheese
Fresh thyme, for garnish
DIRECTIONS
1. Preheat the oven to 350°F and lightly coat a 9 × 13-inch baking dish with cooking spray. Line a baking sheet with parchment paper.
2. In a large saucepan, melt the butter over medium heat. Add the onions and cook, stirring occasionally, until the onions are soft and golden. Halfway through the cooking, around 2 minutes, add the sugar to help the onions caramelize. When the onions are done, add the chicken and beef broths, thyme, mustard, salt, and pepper. Simmer for 5 to 10 minutes.
3. Place the bread slices on the parchment-lined baking sheet and toast 2 to 3 minutes on each side.
4. Place half of the bread slices in the baking dish, overlapping slightly.
5. Layer half of the onion mixture on top of the bread slices. Top with remaining bread slices, then the remaining onion mixture. Cover with the cheese. Cover with foil and bake until hot and bubbling, 30 to 35 minutes. Garnish with fresh thyme and serve.