Chocolate Sour Cream Cupcakes with Chocolate Buttercream

Ingredients

• 1 18.25-oz package German chocolate cake mix
• 1 container (16 oz) Sour cream
• 1/4 cup unsalted butter (1/2 stick), melted
• 2 large Eggs at room temperature
• 1 teaspoon Pure vanilla extract
• Vegetable cooking spray
• 1/2 cup unsalted butter (1 stick), softened
• 1 package (3 oz) Cream cheese
• 1 16-oz package confectioners' sugar sifted
• 1/4 cup Whole Milk
• 6 ounce dark chocolate morsels (1 cup), (see note)