Preheat oven according to cake mix package directions (typically 350°F/175°C). Grease a 9x13-inch baking pan.

Prepare chocolate cake batter according to package instructions. Pour into prepared pan and bake according to package directions until a toothpick comes out clean.

While cake is still hot, use wooden spoon handle to poke holes all over the surface, spacing about 1 inch apart and going almost to the bottom.

Whisk together sweetened condensed milk and half of the chocolate fudge sauce. Pour slowly over warm cake, ensuring mixture seeps into all holes. Let cool completely.

Toast coconut and pecans in a dry skillet over medium heat for 3-5 minutes, stirring frequently until golden and fragrant. Remove from heat and cool completely.

Beat heavy cream with electric mixer until it thickens. Add powdered sugar and vanilla, continuing to beat until stiff peaks form.

Gently fold toasted coconut and pecans into whipped cream. Spread evenly over cooled cake.

Warm remaining chocolate fudge sauce slightly until pourable. Drizzle over coconut-pecan layer. Sprinkle with additional pecans and coconut.

Refrigerate for at least 2 hours before serving to allow flavors to meld and layers to set.