Combine first 4 ingredients in a small bowl; brush over salmon. Dredge salmon in sesame seeds.
Heat oil in a nonstick skillet over medium-high heat; add salmon, and cook 4 minutes on each side or until desired degree of doneness.
Split baguette; toast, if desired.
Spread Wasabi Mayonnaise on bread; layer spinach, salmon, and cucumber. Cut into 4 pieces.