Prepare the oven and pans.
Preheat the oven to 350°F. Grease your cake pans and line the bottoms with parchment paper.
Two boxes of cake mix make a generous amount of batter. Use deep 8-inch pans only if they provide enough capacity, or divide among additional pans. Fill each pan no more than two-thirds full.
Mix the batter.
In a large bowl, whisk together the melted butter or oil, milk, and eggs until combined.
Add the vanilla cake mixes, dry coconut pudding mixes or coconut extract, and 1 cup coconut flakes. Mix for 1–2 minutes, scraping down the bowl as needed, just until evenly combined.
Bake.
Divide the batter evenly among the prepared pans.
Begin checking at 30–35 minutes. The cakes are ready when the centers spring back lightly and a toothpick comes out clean or with a few moist crumbs. Deeper layers may need considerably longer.
Cool and chill.
Let the cakes cool in their pans for 10–15 minutes. Carefully turn onto wire racks, remove the parchment, and cool completely.
Wrap the cooled cakes and refrigerate for a couple of hours, or freeze briefly until firm enough to slice easily.
If you baked two sufficiently thick layers, slice each horizontally to create four layers. You can also leave them whole.
Make the frosting.
Beat the softened butter until creamy. Add the cream cheese and beat just until smooth.
Add the coconut extract, then gradually mix in the powdered sugar on low speed. Scrape down the bowl and mix briefly until creamy and spreadable.
If the frosting feels too soft for layering, refrigerate until it firms slightly.
Assemble the cake.
Place the sturdiest cake layer on a serving plate. Spread with frosting and sprinkle with some of the decorating coconut.
Repeat with the remaining cake layers, frosting, and coconut, reserving enough frosting to cover the outside.
Finish and refrigerate.
Spread the remaining frosting over the top and sides. Gently press the remaining coconut flakes onto the outside.
Refrigerate until the frosting is firm and keep chilled until serving. Let slices stand briefly at room temperature for a softer texture.