Preheat the oven to 325℉ (163℃). Spray a 12 to 15-cup Bundt pant with baking spray. If using a smaller bundt pan like the 10-cup heritage bundt pan shown in the post, you might want to use some of the batter to make about 3-4 cupcakes or the pan could overflow and your baking time will need to be increased by about 10 minutes.
In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
3 cups (423g) all-purpose flour, 1 teaspoon baking powder, ½ teaspoon salt
In a large bowl, beat the butter, shortening, brown sugar, and vanilla on medium-high speed using the paddle attachment for 3 to 5 minutes or until light and fluffy.
1 cup (227g) salted butter, ½ cup vegetable or canola oil, 3 cups (600g) packed brown sugar, 2 teaspoon pure vanilla extract
Add the eggs one at a time, mixing well between each addition, until combined. Stop to scrape the bottom and sides of the bowl.
5 large eggs
Add the flour mixture alternately with the buttermilk, about 1/2 of each at a time, mixing on low speed between each addition just until combined. Stir in the pecans by hand.
1 cup buttermilk, 1 cup coarsely chopped pecans
Spoon the batter into the prepared pan. Bake for 50 to 60 minutes, or until a cake tested inserted into the center of the cake comes out clean with just a few crumbs clinging to it.
Remove the cake from the oven and let it cool on a wire rack for 10 minutes. Invert the cake onto the rack to cool completely.
Meanwhile, make the praline icing by combining butter, brown sugar, and milk in a medium saucepan over medium-high heat. Bring to a boil, whisking constantly. Boil for 1 minute while stirring constantly, then remove from the heat and whisk in the powdered sugar and vanilla. Keep stirring for about 5 minutes until the icing is smooth and has thickened.
½ cup (113g) salted butter, 1 cup (200g) light brown sugar, ¼ cup whole milk, 1 cup powdered sugar, 1 teaspoon pure vanilla extract
Drizzle the icing over the cooled cake. Decorate with whole or chopped pecans. The frosting will harden and set to a fudgy praline texture when it cools.