Preheat the oven to 350 degrees F. Line 24 muffin cups with paper liners.

In a medium saucepan, combine the butter, cocoa powder, chocolate and espresso powder. Cook over low heat, stirring constantly, until the chocolate melts and the mixture is smooth. Let cool for 20 minutes.

In a large bowl, beat the sugar and eggs at medium-high speed with a mixer until fluffy.

In a medium bowl, combine the flour, salt, baking powder and baking soda. Gradually add to the sugar mixture, beating until combined. Add the chocolate mixture, stirring until smooth. Stir in the sour cream.

Spoon the batter into the prepared muffin cups. Bake until a wooden pick inserted in the center comes out clean, 12 to 14 minutes. Let cool in the pans for 10 minutes. Remove from the pans and cool completely on wire racks.

Pipe or spread Creamy Espresso Frosting over each cupcake. Top with a chocolate covered espresso beans if desired.

In a large bowl, combine the cream and espresso powder, stirring until the espresso powder dissolves. Add the butter and beat at medium speed with a mixer until creamy. Gradually add confectioners' sugar, beating until smooth.