For the Cupcakes: 

1. Preheat the oven to 350°F. Line a cupcake pan with cupcake liners.
2. Toast the pecans on a baking sheet for about 5 minutes, longer if the oven is not fully preheated. Cool the pecans and then chop them into fine pieces.
3. In a large mixing bowl, combine the sugar, brown sugar, vegetable oil, eggs and egg yolks, and vanilla extract. Beat on medium speed until the eggs and oil are well incorporated and the batter is lighter in color, about 2 minutes. Scrape down the bowl as needed.
4. Next, mix in the sour cream and beat until well combined.
5. In a medium-sized bowl, combine all remaining dry ingredients. Then, add half the dry ingredients to the batter, followed by half the buttermilk, and beat until it starts to combine.
6. Finally, add the remaining dry ingredients, mixing on low speed while pouring in the buttermilk and beating until all of the ingredients are well combined.
7. Use a spatula to scrape down the sides of the bowl and stir the batter from the bottom to the top to ensure it’s well mixed. Add the chopped pecans and fold into the cupcake batter.
8. Using a large cookie scoop, divide the batter evenly, filling each liner 2/3 full.
9. Bake at 350°F for 14-16 minutes. Test the cupcakes for doneness by inserting a toothpick into the center of the cupcake. If the toothpick comes out clean, the cupcakes are done. Cool Completely.

For the Frosting:

1. Cut the butter into pieces. Using the paddle attachment, whip butter for 5-7 minutes, scraping down the bowl occasionally. Beat until the butter looks light in color.
2. Add 3 cups of powdered sugar and mix on low speed until incorporated into the butter, then add the vanilla extract and mix to combine. Beat for about 60 seconds.
3. Next, add another 2 cups of powdered sugar, the brown sugar, and the maple syrup, and beat on low speed until sugar is incorporated. Increase speed to medium-high and beat for 2-3 minutes.
4. Add the remaining powdered sugar and heavy cream. Beat on low until ingredients start to mix. Increase speed to medium-high and beat for another 2-3 minutes to whip additional air into the frosting. If the frosting is too thick, add a tablespoon of heavy cream and continue beating until fluffy.
5. Frost the cooled cupcakes using a large open star tip and garnish with leftover crushed pecans. Store in an airtight container.