Preheat oven to 350.
Make cake batter according to box directions.
Pour into 4 oz Mason jars filling a little less than half full.
Place jars on baking sheet and bake for 18 minutes.
Allow to cool completely.
Cream butter, vanilla and powdered sugar in mixing bowl.
Slowly add milk until desired consistency icing is reached.
Ice the tops of cakes.
Sprinkle with candy decorations and place a chocolate bunny on the top of each.