Optional: Toast the bread.
Spread Dijon mustard evenly over one side of each slice.
Layer with arugula, brie, and ham.
Close the sandwiches with the remaining bread slices, mustard side down, and press gently to set.
Combine the sparkling water, orange slices and chia seeds. Stir thoroughly, let sit for 2–3 minutes, then stir again to prevent clumping.
Serve the sandwich with carrots, hummus, pickle, and orange chia sparkling water.