The delicious filling comes from cooked mangoes. Add fruit chunks (fresh or frozen mangoes) to a small pot on the stove. After cooking 5 minutes, add lemon juice, sugar, and salt to pot and let it cook for 16-20 more minutes. Mango's texture will resemble cooked apples.
Let the fruit cool before adding it to the cupcakes, which should also be room temperature. You can use a cupcake corer or do what I did and make a hole in each cupcake using the wider opening of a piping tip.
If you haven't used freeze dried fruit in frosting, you're in for a treat. Freeze dried mangoes have a concentrated, more intense flavor than fresh or even dried fruits. Their powder works well in frosting because it doesn't add excess moisture.
Beat unsalted butter, powdered sugar, vanilla and coconut extracts, salt, freeze dried mango powder, and heavy cream (or coconut milk) on low for about 30 seconds before increasing speed to medium high for 5 minutes.