Preheat your oven to 350°F (175°C) and line a muffin tin with cupcake liners.
In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.
Add the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.
In another bowl, combine the flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the butter mixture, alternating with the buttermilk, starting and ending with the dry ingredients.
Fold in the toasted pecans until evenly distributed.
Divide the batter evenly among the cupcake liners, filling each about two-thirds full.
Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cupcakes to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.
For the frosting, beat the softened butter in a bowl until creamy.
Gradually add the powdered sugar, mixing until smooth.
Stir in the vanilla extract and heavy cream until the frosting reaches your desired consistency.
Once the cupcakes are completely cool, frost them generously with the buttercream and sprinkle the tops with additional toasted pecans.