Spread the softened butter evenly on one side of each slice of bread.
Place two slices of bread butter-side down on a cutting board.
Spread 1 tablespoon of blueberry preserves over each slice.
Layer the sliced Brie evenly over the preserves.
Sprinkle the fresh blueberries over the Brie.
Add fresh thyme leaves and drizzle with honey if using.
Top with the remaining bread slices, butter-side facing up.
Heat a large skillet over medium-low heat.
Cook the sandwiches for 3–4 minutes until the bread is golden brown and crisp.
Carefully flip the sandwiches and cook for another 3–4 minutes, until the second side is golden and the Brie has fully melted.
Transfer to a cutting board and let the sandwiches rest for 1 minute.
Slice in half and serve immediately.