Make the simple syrup by heating 3/4 cup sugar with 1 cup water in a small saucepan until sugar is completely dissolved. Add the juice of five lemons and pour both into a pitcher. Add 3 to 4 cups of cold water and 8 to 10 ounces peach schnapps. Refrigerate for at least 30 minutes. Pour over crushed ice before serving and garnish with fresh mint leaf.