Preheat oven to 375 and fire up grill. Place sliced ciabatta in a single layer on a baking sheet and drizzle with olive oil. Bake for 10-12 minutes or until top is beginning to turn golden brown.
While ciabatta is toasting, slice peaches into discs. Brush both sides of the peach slices with oil. Over medium low heat, grill peach slices for about 2-3 minutes on each side or until grill lines appear.
Crush shelled pistachios roughly using mortar and pestle, or place into a plastic bag and use a wooden spoon to crush. Wash 10 mint leaves and slice into skinny ribbons.
Remove ciabatta from oven & generously spread Boursin Cracked Black Pepper. Layer grilled peach discs on each ciabatta slice. Sprinkle crusted pistachios & mint ribbons on top. Drizzle balsamic reduction on top of each crostini for finishing touch.