In a medium-high heated saucepan, melt 2 tablespoons of butter. Once melted, add your sliced baby Bella or cremini mushrooms. Sauté for about 5 minutes, allowing the mushrooms to sweat and release their moisture.

Incorporate 2 tablespoons of minced garlic into the pan with the mushrooms. Continue to sauté for about 10 more minutes until the mushrooms are browned and all liquid has evaporated.

While the mushrooms finish cooking, preheat your broiler to high.

Spread a layer of whole grain Dijon mustard on one side of each slice of thick rustic French bread.

Layer your mustard-dressed bread with a sprinkle of shredded Swiss cheese, followed by the sautéed mushrooms, and top with more Swiss cheese.

Carefully place the assembled toasts under the preheated broiler for about 2 minutes.

Once broiled, remove the toasts from the oven and sprinkle fresh thyme leaves over the top. Season with salt and pepper to taste.