Preheat the oven to 350 degrees F. Line a 6-cup muffin pan with paper liners.

Whisk the cocoa powder with 1/3 cup hot water in a bowl until smooth.

Whisk in the chocolate syrup until smooth and let cool slightly.

In a large bowl, whisk together the flour, granulated sugar, baking soda, baking powder, and salt.

In a separate bowl, whisk together the vegetable oil, egg, milk, and vanilla extract.

Add the wet ingredients to the dry ingredients and fold until just combined.

Divide the batter evenly among the prepared muffin cups.

Bake for 18 to 20 minutes, or until a toothpick inserted into the center comes out clean.

Let the cupcakes cool in the pan for 10 minutes before transferring them to a wire rack to cool completely.

To make the frosting, put the chopped milk chocolate in a microwave-safe bowl and microwave on 70% power in 30-second intervals, stirring in between, until melted and smooth.

Let the melted chocolate cool slightly.

In a large bowl, beat the unsalted butter, vanilla extract, and confectioners' sugar with a mixer on medium-high speed until fluffy.

Add 3 tablespoons of whole milk and beat until smooth, about 3 minutes.

Remove half of the frosting to a separate bowl.

Add the cocoa powder, melted chocolate, and a pinch of salt to one bowl of frosting and beat until fluffy, about 2 minutes.

Mix the remaining 1 tablespoon of whole milk and the malted milk powder in a cup.

Add the milk mixture and another pinch of salt to the remaining plain frosting and beat until fluffy, about 2 minutes.

If the frosting is too soft, cover it and chill it in the refrigerator until it is firm enough to pipe.

Frost the cupcakes using a piping bag or knife.

Top each cupcake with small pretzel rods.