For the white chocolate cups:
Place your white chocolate chips in a double boiler (if you don't have a double boiler, fill a saucepan with 1-2 inches of water and place a bowl on top...add your chocolate chips to that bowl)
Add 2 tsp vegetable oil to the chips
Cook over medium heat, stirring frequently, until chips are melted
Pour into mold and refrigerate for 1/2 hour
For the mousse:
Combine sweet and semi-sweet chocolate in a saucepan
Melt over medium heat, stirring frequently
Cool until lukewarm
Beat cream at medium speed until foamy
Gradually add powdered sugar, beating until soft peaks form
Gently fold whipped cream into chocolate,
Remove white chocolate cups from mold
Using a spoon or a frosting bag (recommended), fill each white chocolate cup with mousse.
Enjoy!