Melt the butter in a medium saucepan over medium heat.
Mix in garlic and almonds, heating until almonds are lightly browned. Stir in mushrooms and cook until tender, about 5 minutes. Cover with brandy and sprinkle with tarragon.
Place Brie in a small baking dish.
Pour the mushroom and brandy mixture over Brie.
Bake in the preheated oven 20 minutes, or until bubbly.