Place the bacon in a large skillet or griddle and cook until golden brown and crisp. Remove to a paper towel-lined plate. Break each piece into fourths and set aside.
Heat a cast iron griddle or cast iron pan over medium heat.
Spread butter on 1 side of each slice of bread. Layer 4 of the slices of the bread with 3 to 4 slices of brie, 2 tomato slices, watercress, 2 slices goat cheese, and 4 slices of broken up bacon and season with salt and freshly ground black pepper. Place the remaining bread slices on top, butter side up and cook on the griddle until golden brown on both sides and the brie has melted.