Preheat the oven to 350°F. Toast the pecans on a baking sheet for about 5-7 minutes. Cool the pecans and then chop into fine pieces.
2 cups pecans
Using a stand mixer, blend the sugar, brown sugar, vegetable oil until well combined. Add in eggs and egg yolks and beat on medium speed until the eggs are well incorporated and the batter is lighter in color, about 2 minutes.
2 ½ cups sugar, ½ cup dark brown sugar, ¾ cup vegetable oil, 3 large eggs, 3 large egg yolks
Next mix in the sour cream and beat until well combined.
¾ cup sour cream
In a medium sized bowl, whisk flour, baking powder, soda and salt.
3 cups flour, 3 teaspoon baking powder, ¾ teaspoon baking soda, 1 teaspoon salt
Measure buttermilk into a 4 cup measuring cup. Add the vanilla.
2 cups buttermilk, 1 Tbls vanilla extract
Then, add 1/3 of the dry ingredients to the batter followed half the buttermilk and beat until it starts to combine. Alternate adding the remaining flour and buttermilk, starting and ending with the flour. Blend until just combined.
Add the chopped pecans and fold into the cupcake batter. Using a large ice-cream (cookie) scoop, fill each cupcake liner 2/3 full.
Bake at 350°F for 18 minutes, turning halfway through.