In a saucepan, roast the pecan on medium heat, stirring regularly for 2 minutes, until they start to be fragrant. Reduce the heat to low and add the maple syrup. Continue cooking for 10 minutes until the syrup starts to crystallize on the pecans, stirring regularly. Let cool on parchment paper.
Put the chopped dark chocolate in a medium-size bowl and set aside.
In a saucepan, heat the cream with the vanilla bean over medium-low heat until simmering, about 5 minutes. Pour the hot cream over the chocolate. Stir until totally smooth. Roughly chop the maple sugar pecans and add them to the chocolate mixture.
Put the bowl of chocolate mixture in an ice bath. Using a spatula, stir it constantly for 5 minutes, then put in the refrigerator for 10 minutes.
After the mixture has chilled, remove it from the refrigerator. Wearing latex gloves and using 2 spoons, scoop out rounded sections of the chocolate into palms and form into balls. Use spoons to roll each ball in the melted chocolate then in the maple flakes. Place on a baking tray covered with parchment paper. Chill until firm, about 1 hour.
Do ahead. The truffles can be made 1 week ahead. Store in an airtight container and keep chilled. Let stand at room temperature 1 hour before serving.