Heat the oven to 350 degrees. Line 18 muffin cups with muffin liners. Melt the chocolate in a microwave-safe bowl for 30 seconds or until almost melted; stir. Continue microwaving at 10 second intervals or until almost melted; stir until smooth. Cool to room temperature. Whisk the flour, cocoa, baking powder, baking soda and 1/2 teaspoon salt in medium bowl. Beat brown sugar, sugar, oil and 1/4 cup softened butter in a large bowl at medium speed for 2 minutes. Reduce speed to low; beat in ¾ cup sour cream and the melted chocolate. Beat in the eggs, one at a time, beating until well blended. Alternately beat in the flour mixture with the milk; beginning and ending with the flour mixture. Divide between the muffin cups. Bake for 20 to 25 minutes or until a toothpick inserted in the center comes out clean. Cool in the pan on a wire rack for 10 minutes; remove the cupcakes. Cool completely. Meanwhile, place the caramels and 2 tablespoons butter in a medium saucepan; heat over medium-low heat until melted, stirring frequently until smooth. Cool slightly and pour into a large bowl. Beat in the remaining sour cream at medium speed. Slowly beat in the powdered sugar, adding additional if necessary for desired consistency. Using a pastry bag and tip or a zip-top plastic bag with a hole snipped out of the corner, pipe the frosting onto the cupcakes or spread with a small knife. Sprinkle with the sea salt. Garnish as desired.