Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with paper cupcake liners. Set aside.

In a medium bowl, whisk together the sifted all-purpose flour, baking powder, and salt. Set aside.

In a large bowl, using an electric mixer (stand or hand-held) on medium speed, cream together the softened unsalted butter and granulated sugar until light and fluffy, about 3-4 minutes. Scrape down the sides of the bowl as needed.

Add the eggs one at a time, beating well after each addition until fully incorporated. Beat in the vanilla extract.

With the mixer on low speed, gradually add about one-third of the dry ingredients to the butter mixture, mixing until just combined. Then, add half of the milk, mixing until just combined. Repeat with another third of the dry ingredients, followed by the remaining milk, and finish with the last third of the dry ingredients. Mix only until just combined and no streaks of flour remain. Do not overmix.

Divide the batter evenly among the 12 prepared cupcake liners, filling each about two-thirds full. An ice cream scoop works perfectly for this.

Bake for 18-22 minutes, or until a wooden skewer or toothpick inserted into the center of a cupcake comes out clean. The tops should be lightly golden and spring back when gently touched.

Remove the cupcakes from the oven and let them cool in the muffin tin for 5 minutes before transferring them to a wire rack to cool completely. Ensure cupcakes are fully cooled before frosting, which takes about 30-60 minutes.

In a large bowl with an electric mixer, beat the softened butter on medium speed for 3-5 minutes, until very light and fluffy. This step is crucial for silky buttercream.

Gradually add the sifted powdered sugar, about 1 cup at a time, mixing on low speed until combined after each addition. Once all the sugar is added, increase speed to medium and beat for 2 minutes.

Add the heavy cream (or milk), pure vanilla extract, and salt. Beat on medium-high speed for another 2-3 minutes, until the frosting is incredibly smooth, light, and fluffy. If the frosting is too thick, add more cream 1 teaspoon at a time; if it's too thin, add more powdered sugar 1 tablespoon at a time.

Once the cupcakes are completely cooled, frost them generously with the vanilla buttercream using an offset spatula or a piping bag fitted with your favorite tip.

Serve immediately or store for later enjoyment.