Line a baking sheet with parchment paper and coat with 1/2 tablespoon oil and place the mushroom slices on the tray leaving space between each one
Using a pastry brush, brush the top of each slice of mushroom with olive oil and sprinkle with smoked paprika
Place in the oven and bake for 15 minutes flip the mushrooms over and bake for about 8 to 10 minutes more - until they become brown - remove from oven and set aside
Heat a skillet over medium heat with 1 tablespoon olive oil
Spread 2 ounces of brie cheese on top of two slices of bread
top each slice with caramelized onions and mushrooms
add 1 ounce of cheese and top with a slice of bread
place the sandwich in a pan and grill until bread turns golden, flip over and cook until cheese becomes melted and bread is golden brown