Ingredients:
• 1 pound mushrooms, cleaned and sliced
• 1 medium yellow onion, finely diced
• 3 tablespoons olive oil
• 2 tablespoons unsalted butter
• 2 tablespoons all-purpose flour
• 2/3 cup dry white wine
• 1 cup low-sodium chicken broth (or vegetable broth/hot water)
• 2/3 cup heavy cream
• 5 oz (150 g) firm melting cheese (such as Gruyère, Swiss, or Gouda), shredded and divided
• 2 pinches ground nutmeg
• 1/2 tsp freshly ground black pepper
• Kosher salt, to taste
Directions:
• Heat olive oil and butter in a large skillet over medium-high heat.
• Add the diced onion and cook for 3 to 4 minutes until translucent.
• Add the sliced mushrooms and sauté, stirring occasionally, until they release their liquid and brown nicely (about 8 to 10 minutes).
• Pour in the white wine, scraping any fond from the bottom.
• Let it simmer vigorously for 5 to 6 minutes until the liquid reduces down to about 2 tablespoons.
• Reduce heat to medium-low.
• Sprinkle the 2 tablespoons of flour directly over the mushrooms and onions.
• Stir constantly for 1 to 2 minutes to coat the mushrooms and cook out the raw flour flavor.
• Slowly pour in the 1 cup of chicken broth while stirring to prevent lumps.
• Whisk in the heavy cream, nutmeg, black pepper, and salt.
• Simmer gently over low heat for 3 to 4 minutes until the sauce turns thick and glossy.
• Remove from heat and stir in half of the shredded cheese until melted.
• Preheat the oven to 400°F (200°C).
• Divide the mushroom mixture evenly among individual ramekins, traditional cocottes, or a small baking dish.
• Scatter the remaining cheese over the top in an even layer.
• Bake on the upper oven rack for 10 to 12 minutes until bubbling around the edges.
• Switch to the broiler on high for 1 to 2 minutes until the cheese is blistered and golden brown.
• Let rest for 5 minutes before serving.
