Preheat your oven to 375°F (190°C). This ensures that your mushrooms will bake evenly and come out perfectly cooked.
Gently clean the mushrooms using a damp cloth or mushroom brush. Carefully remove the stems and set them aside, as they will be part of the stuffing.
In a large skillet, heat the olive oil over medium heat. Add the finely chopped onion and sauté until translucent, about 5 minutes. Add the minced garlic, ground chicken or turkey, dried thyme, red pepper flakes, salt, and pepper. Cook until the meat is browned and cooked through, stirring occasionally.
Once the meat is cooked, remove the skillet from heat. Stir in the grated Gruyere cheese and breadcrumbs until well combined. The cheese should melt slightly and create a creamy mixture.
Using a spoon or small cookie scoop, fill each mushroom cap with the chicken and cheese mixture, packing it in gently but firmly.
Place the stuffed mushrooms on a baking sheet lined with parchment paper. Bake in the preheated oven for about 20-25 minutes, or until the mushrooms are tender and the tops are golden brown.
Remove the stuffed mushrooms from the oven and let them cool for a few minutes. Serve warm and watch them disappear in no time!
