In a small bowl, whisk together vinegar, lemon juice and olive oil. Add the shallots, garlic, capers and olives. Stir to combine.
Prep remaining ingredients. Cut baguette into 4 equal serving sizes, slit each in half lengthwise and remove some of the bread inside to make room for fillings.
Spread top half of each bread with boursin cheese and then add chunks of smoked salmon.
Spread bottom half of each with some of the vinaigrette with shallots, capers and olives. top with egg slices, then tomatoes, then pepper slices and arugula.
Drizzle both top and bottom halves with more of the vinaigrette. carefully place top onto bottom without spilling out the ingredients to make sandwich.
wrap each sandwich tightly with parchment paper and hold together with string. Let sandwiches rest in the refrigerator for at least 2 hours or up to 24 hours to allow flavors to marry. Enjoy!