Instructions
Travel to the Poffin House and create Poffins that correspond to the statistic you want to enhance. For example, if you want to raise your Pokémon's Toughness level, you would make Sour Poffins with Aspear, Sitrus, Wepear or Rowap Berries.
Feed your Pokémon the correct type of Poffin until the correct statistic reaches its maximum level.
Run to Pastoria City and speak with Scarf Guy. If one of your Pokémon is maxed, he will offer you a scarf that corresponds to the statistic.
Collect all five scarves by making Poffins and maxing out each individual stat on different Pokémon. You will find Yellow for Toughness, Blue for Beauty, Pink for Cute, Orange for Cool and Green for Smart.