Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with cupcake liners.
Cream the butter and sugar together until light and fluffy.
Add the eggs one at a time, mixing well after each addition.
Add the vanilla bean paste and mix until combined.
In another bowl, whisk together the flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, alternating with the milk. Begin and end with the dry ingredients. Mix until just combined.
Scoop the batter into the lined muffin tin, filling each cup about 2/3 full.
Bake for 18-20 minutes or until a toothpick inserted in the center comes out clean.
Remove the cupcakes from the oven and let them cool in the tin for 10 minutes. Then transfer them to a wire rack to cool completely.
For the buttercream, beat the softened butter until creamy. Gradually add the powdered sugar, mixing until well combined. Add the vanilla bean paste and heavy cream, and continue to beat until the frosting is smooth and fluffy.
Once the cupcakes are cool, frost each cupcake generously with the vanilla buttercream.