For caramel, in a medium heavy saucepan, stir together the 1/4 cup whipping cream, the butter, brown sugar, and corn syrup. Bring to a boil over medium-high heat, whisking occasionally; reduce heat to medium. Boil gently for 2 minutes more. Remove from heat; stir in vanilla. Set aside while preparing chocolate mixture.

Place water in a small bowl. Sprinkle gelatin over the surface. Let stand for 5 minutes to soften.

For chocolate mixture, in a medium saucepan, combine the 1 cup whipping cream and the granulated sugar. Heat over medium-low heat until the mixture almost comes to a boil. Remove from heat. Add softened gelatin; stir until it dissolves. Add Ghirardelli® 60% Cacao Bittersweet Chocolate Baking Chips. Let stand for 5 minutes. Stir to mix in chocolate. Whisk in sour cream.

Fill twelve 2-ounce shot glasses, ramekins, or other small dessert dishes 1/3 to 1/2 full of chocolate mixture. Chill for 20 minutes or until just set. Divide caramel evenly among the glasses; chill for 15 minutes. Spoon on or pour in the remaining chocolate mixture. Chill for at least 30 minutes.

In a small bowl, beat the 1/4 cup whipping cream and the powdered sugar until soft peaks form (tips curl). To serve, top each panna cotta with a dollop of whipped cream, and, if desired, a piece of Ghirardelli Milk & Caramel SQUARES™ Chocolate.

For easier cutting, place Ghirardelli Dark & Raspberry SQUARES™ Chocolates in a single layer on a baking sheet. Freeze for at least 30 minutes. Using a sharp knife, cut squares into quarters.