Preheat the oven:
Preheat your oven to 350°F (175°C). Line a muffin tin with cupcake liners.
Mix the dry ingredients:
In a medium bowl, whisk together the flour, baking powder, and salt.
Prepare the batter:
In a large mixing bowl, beat the butter and sugar until light and fluffy. Add the eggs, one at a time, beating well after each addition. Stir in the vanilla extract.
Combine wet and dry ingredients:
Gradually add the dry ingredients to the wet mixture, alternating with the milk, starting and ending with the dry ingredients. Mix until just combined.
Add blueberries and chocolate:
Gently fold in the blueberries and white chocolate chips. Be careful not to overmix.
Bake the cupcakes:
Divide the batter evenly among the cupcake liners, filling each about 2/3 full. Bake for 18–22 minutes, or until a toothpick inserted into the center comes out clean. Allow the cupcakes to cool completely on a wire rack before frosting.
Make the frosting:
In a mixing bowl, beat the butter until smooth. Gradually add the powdered sugar, melted white chocolate, vanilla, and cream, beating until fluffy and spreadable. Add more cream if needed to reach your desired consistency.
Frost the cupcakes:
Use a piping bag or a spatula to frost the cooled cupcakes. Garnish with additional blueberries or white chocolate shavings if desired.