Preheat the oven to 350°F and line a baking sheet with parchment paper for easy cleanup.

Cut the mushrooms, then chop the onions and parsley, and set aside.

Slice the baguette into 25 pieces, about ¼-½ inch thick. Arrange the slices in a single layer on the prepared baking sheet.

Heat the olive oil in a skillet over medium-low heat. Add the onions and cook for 2-3 minutes, stirring often until softened. Stir in the garlic and cook for another 30 seconds.

Add the chopped mushrooms to the pan and sauté for about 5 minutes, until the liquid has cooked off and the mushrooms are tender.

Place a small amount of the Gruyere cheese on each slice of bread, then spoon some of the mushroom mixture on top.

Sprinkle with more cheese to cover the mushrooms.

Transfer the baking sheet to the oven and bake for 5-6 minutes, or until the cheese is melted and bubbling.

Remove from the oven and sprinkle with fresh parsley.

Serve warm and enjoy!