Preheat the Oven and Prepare the Bundt Pan: Begin by preheating your oven to 350°F (175°C). Grease a Bundt pan generously with non-stick cooking spray to ensure the cake does not stick after baking. Set the pan aside.
Prepare the Cake Batter: In a medium-sized mixing bowl, combine the chocolate cake mix, milk, melted butter, and eggs. Using either a hand mixer or stirring by hand, mix the ingredients until the batter is smooth and well-combined. Once ready, pour the prepared batter into the greased Bundt pan, ensuring it is evenly distributed.
Bake the Cake: Place the Bundt pan into the preheated oven and bake for 45 to 50 minutes. The cake is done when a toothpick inserted into the center comes out with only a few moist crumbs attached. Allow the cake to cool in the pan for approximately 10 minutes before carefully inverting it onto a cake plate to cool completely.
Prepare the Frosting: While the cake is cooling, prepare the frosting. In a small saucepan, combine the butter, cocoa powder, and milk. Heat over medium heat, whisking frequently, until the butter has melted and the mixture is smooth. Remove from heat and gradually add the powdered sugar, continuing to whisk until the frosting is smooth and glossy. Stir in the chopped pecans until fully incorporated.
Frost the Cake: Once the cake has completely cooled, pour the chocolate pecan frosting over the top of the Bundt cake, ensuring an even layer. Allow the frosting to set before slicing and serving.
Storage: To store any leftover cake, cover it with plastic wrap and refrigerate for up to 4 days to maintain freshness.