Make the cupcakes: Preheat the oven to 350˚. Line a 12-cup muffin pan with paper liners. Whisk the flour, baking soda and salt in a medium bowl.
Heat the milk in a small saucepan over medium heat until hot but not boiling. Pour over the cocoa powder in a large bowl and whisk until smooth. Let cool slightly. Whisk in the granulated sugar, vegetable oil, egg, vanilla and orange zest until smooth. Whisk in the flour mixture until just combined.
Divide the batter among the prepared muffin cups. Bake until a toothpick inserted into the centers comes out clean, 20 to 25 minutes. Let cool 5 minutes in the pan, then remove the cupcakes to a rack to cool completely.
Meanwhile, make the frosting: Place the chocolate chips in a small microwave-safe bowl. Microwave in 30-second intervals, stirring, until smooth, 2 to 3 minutes. Let cool 3 minutes. Combine the butter, confectioners' sugar, milk, cocoa powder and vanilla in a food processor and process until fluffy, 1 minute. Add the melted chocolate and process until smooth, 1 minute. Let sit at room temperature about 30 minutes to firm up.
Transfer the frosting to a piping bag fitted with a 1/2-inch round tip. Pipe the frosting on the cupcakes about 2 1/2 inches high. Starting at the bottom, stick in cereal squares at a 45-degree angle to cover the frosting.