1. Preheat oven to 350 F degrees. Line and grease a 9x13 cake pan with parchment paper.
2. In a stand mixer or using a hand mixer, cream together sugar and butter for 3 minutes. Add the eggs, one by one, and mix until combined. Add vanilla extract.

3. In another large bowl, whisk together the flour, baking powder, salt and butterscotch pudding mix. Slowly add the flour mixture to the wet ingredients. Then add buttermilk and mix until just combined. Fold in the butterscotch chips and nuts with a spatula.

4. Spread batter into prepared pan and bake for 30-35 minutes or until a toothpick poked in the center comes out clean. Remove pan from oven and allow to cool for 15 minutes before transferring to wire rack to cool completely.

Make the Butterscotch Glaze:

1. In a heavy-bottomed saucepan over medium heat, add butter until melted. Stir in brown sugar, and heavy cream with a wooden spoon or heat-proof spatula. Bring the mixture to a boil, scraping down the sides occasionally, and boil for 4 to 5 minutes.
2. Remove pan from heat and stir in vanilla; allow to cool. The mixture will thicken more as it cools.

Make the Frosting:

1. In a small pot over medium heat, combine brown sugar and milk and bring to a boil. Allow to bubble for 3-4 minutes, stirring constantly. Remove from heat and stir in butter.
2. Stir in 1½ cups powdered sugar and whisk or beat with a mixer until smooth. If frosting is too thin, add more sugar, a little bit at a time because frosting will harden as it sets. Spread frosting evenly on cake. Top with a drizzle of butterscotch glaze and toasted chopped pecans.