Preheat your oven to 350°F (175°C) and prepare a 15x10-inch jelly roll pan by greasing it and lining the bottom with parchment paper.

In a large mixing bowl, sift together all-purpose flour, granulated sugar, cocoa powder, baking powder, baking soda, and salt until evenly mixed.

In a separate bowl, whisk together the eggs, whole milk, vegetable oil, and vanilla extract until well combined, then slowly incorporate into the dry mixture.

Carefully stir in boiling water until just combined, creating a thin batter.

Pour the batter into the prepared jelly roll pan and bake for 15 to 20 minutes, or until a toothpick comes out clean.

Let the cake cool in the pan for about 5 minutes, then invert onto a powdered sugar-dusted kitchen towel and remove parchment.

For the filling, combine shredded coconut, chopped pecans, sweetened condensed milk, and vanilla extract in a saucepan and cook until thickened.

Spread the cooled filling over the cake, then roll the cake tightly using the towel and refrigerate for 1 hour.

Whip the heavy cream with powdered sugar and vanilla extract until stiff peaks form.

Unwrap the cake roll, place seam-side down, and spread the whipped cream frosting over it, garnishing if desired.