Preheat oven to 350 degrees F. Place baguette slices on rimmed baking pan and spray with cooking spray. Bake 8 to 10 minutes or until crisp, turning once. Meanwhile, use mixer to whip cream cheese, blue cheese, lemon juice and pepper until well combined and fluffy.
Heat oil in large skillet over medium heat. Add shrimp and cook 4 to 6 minutes or until opaque and cooked through; stirring occasionally. Remove from heat and stir in buffalo sauce. Spread blue cheese mixture on crostini; divide mixed greens over crostini.
Place 1 shrimp on each crostini and garnish with additional blue cheese, if desired. Serve immediately.