Heat Cream, Sugar, and Butter - In a heavy-bottom pot, heat the heavy whipping cream, sugar, and butter. Heat until the sugar is completely melted and the mixture is well combined.
Combine Cornstarch, Vanilla, and Water - In a small bowl, combine the cornstarch, vanilla, and one tablespoon of water.
Combine the Cornstarch Mixture With the Cream Mixture - Pour the cornstarch mixture into the heavy cream mixture. Whisk to combine and bring the ingredients to a boil in the heavy-bottom pan. Continue cooking for about one minute, until the mixture becomes thick.
Remove From Heat and Add the Coconut - Remove the heavy-bottom pan from the heat and stir in the sweetened, shredded coconut. Allow the mixture to completely cool.
Fill Cupcakes - Using a cupcake corer or butter knife, carve a shallow hole into each cupcake. Using a spoon, fill the cupcakes with coconut filling. Top the cupcake with your favorite frosting and serve.