Slice bread into 1/2 inch thick slices and cut each slice in half, crosswise. Toast the bread on a medium setting. Remove from toaster and smear with mustard. Top with 2 slices of apple and some grated cheddar.
Place the crostini under the broiler for 1-2 minutes, watching closely to ensure it doesn't burn. Remove from broiler and drizzle with rosemary honey. Garnish with additional fresh rosemary.