Preheat oven to 350ºF. Spoon strawberry preserves into a microwave safe bowl microwave on HIGH for 30 seconds. Stir in balsamic vinegar, salt, pepper, chopped spinach and dried blueberries. Toss and stir to coat.
Slice Brie in half horizontally. Place bottom half of Brie on baking sheet. Mound spinach mixture on cut side of Brie. Replace with top half of Brie, rind side up; press down slightly. Top with walnut pieces. Bake 6 to 8 minutes or until the Brie is soft. Drizzle with additional heated preserves, if desired. Top with a sliced strawberry, if desired. Serve warm with toasted baguette slices.