Instructions
Wander the game world and pick berries. You'll find hundreds of them scattered throughout the game world, especially in wild areas, like the routes connecting cities. In particular, you're looking for Charti, Chesto, Micle, Oran, Pamtree and Wiki berries.
Travel to Hearthome City, which is north on Route 212, west on Route 209 and east on Route 208. Enter the Poffin House on the west side of town. Here you can transform your berries in Poffins.
Speak with the woman by the Poffin Pot and give her one of your berries. She'll ask you to stir the pot. Use the stylus and touch screen to stir it until the speckles appear in the dough and it turns brown. The poffin is then ready.
Feed the poffin to one of your Pokemon to improve its beauty. Do this several times to max out its beauty stat.
Go to Pastoria City, which is east on Route 212 and west on Route 213. Enter the eastern most house and speak with the man inside. He'll praise your Pokemon for its beauty and give you the Blue Scarf.