Preheat your oven to 350°F (175°C). Grease and lightly flour a 10- to 12-cup Bundt pan, or use baking spray for easy release.
In a large mixing bowl, beat together the chocolate cake mix, whole milk, melted butter, and eggs for about 2 minutes, until the batter is smooth and well combined.
Pour the batter evenly into the prepared Bundt pan, using a spatula to level the top.
Bake for 35–40 minutes, or until a toothpick inserted into the center comes out clean or with just a few moist crumbs. Avoid overbaking to keep the cake tender.
Let the cake cool in the pan for 10 minutes, then carefully invert it onto a wire rack to cool completely.
For the frosting, melt the butter in a small saucepan over medium heat. Whisk in the cocoa powder and milk until the mixture is smooth and just begins to simmer. Remove from heat.
Stir in the powdered sugar, vanilla, and salt until the frosting is glossy and lump-free. Gently fold in the chopped pecans.
Let the frosting cool for 2–3 minutes, then slowly pour it over the cooled Bundt cake, allowing it to drip naturally down the sides.
Let the frosting set for 15–20 minutes before slicing and serving.
