First, mix yogurt with 2 tablespoons maple syrup until smooth. Wash, peel, core and cut pears into thin wedges.
Toast bread slices or fry them in a pan with olive oil.
Spread the bread with yogurt, top with the pear wedges and sprinkle with the hazelnuts and lemon balm.
Drizzle the remaining maple syrup over the pear-hazelnut crostini and serve the crostini.