Ingredient:

• 1 package yellow cake mix (regular size)
• 2 tablespoons butter
• 4 medium tart apples, peeled and finely chopped (about 4 cups)
• 3/4 cup packed brown sugar
• 1 tablespoon cornstarch
• 1 tablespoon water
• 1 cup butter, softened
• 3 cups confectioners' sugar
• 2 tablespoons heavy whipping cream
• 1 teaspoon vanilla extract
• 1-1/2 teaspoons ground cinnamon
• Thinly sliced apples, optional