Preheat the oven to 350 degrees F and line a cupcake pan with 4 liners.
In a mixing bowl, cream the softened butter and sugar until light. Add the egg and vanilla extract, then mix until combined.
Stir in the milk. Add the flour, baking powder, and salt. Mix until the batter is smooth.
Fold in the 1/4 cup white chocolate chips. Divide the batter evenly among the 4 liners.
Bake for 18 to 20 minutes until a toothpick comes out clean. Let the cupcakes cool completely.
Melt the remaining 1/2 cup white chocolate chips in the microwave in short bursts, stirring between each. Dip the pretzel sticks into the melted chocolate to form simple bone shapes and set them on parchment to harden.
Spread or pipe the remaining melted white chocolate over the cooled cupcakes as frosting. Press two bone-shaped pretzels onto each cupcake.