Let the sliced brie sit out at room temperature while you prepare everything else.
Prepare all ingredients per the instructions above.
In a bowl, mix the softened butter, minced chives, parsley, Dijon mustard, and grated garlic until well combined. Season with salt and black pepper to taste.
In another bowl, toss the arugula with lemon juice. Season with salt and black pepper.
Spread the herb butter generously on the inside of the bottom half of the baguette.
Layer the thinly sliced ham and softened brie over the buttered baguette. Season lightly with salt and black pepper.
Top with a handful of arugula, then cover with the remaining half of the baguette.
In a separate pitcher, mix the freshly squeezed lemon juice, water, and sugar until the sugar is fully dissolved. Adjust sweetness to taste.
Serve the sandwich with potato chips, pickle spears, and a glass of lemonade over ice if desired.