Preheat your oven to 350°F (175°C) and grease and flour two 9-inch round cake pans or one 9x13-inch pan.

In a large mixing bowl, cream together the softened unsalted butter, granulated sugar, and brown sugar until light and fluffy (about 3-5 minutes).

Add the eggs one at a time, mixing well after each addition, then add the vanilla extract.

In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add this to the creamed mixture, alternating with the buttermilk.

Fold in the chopped toasted pecans and mix until just combined.

Divide the batter between the prepared pans or pour it all into the 9x13 pan. Bake for 25-30 minutes until a toothpick comes out clean.

Allow cakes to cool in the pans for 10 minutes, then transfer to wire racks to cool completely.

For the icing, beat together cream cheese and softened butter until smooth, gradually adding powdered sugar, and mixing in milk to reach desired consistency.

Frost the cooled cake generously with the cream cheese icing and sprinkle with additional chopped pecans if desired.