Place 12 cupcake liners in a 12 cup muffin pan, set aside. In a large bowl combine the flour, baking powder and salt.
Add in the brown sugar, eggs, milk, butter, pecans and vanilla. Stir just until combined. Divide batter evenly among muffin cups then bake for 18-20 minutes or until toothpick inserted in center comes out clean.
Remove from pan and let cool completely before frosting. To make the frosting: In a small saucepan combine the egg, brown sugar and corn syrup until smooth. Cook over medium low heat stirring constantly until mixture thickens (about 5 minutes). Cool completely.
Add cooled brown sugar mixture and softened butter to the bowl of a stand mixer and beat on high until smooth and light in color, scraping bowl often. (About 5 minutes)
Add in salt and powdered sugar and mix on low until combined then beat on high until smooth and creamy. Spoon into a piping bag fitted with desired tip. Frost cupcakes as desired and sprinkle with chopped pecans.