Combine the hulled strawberries and sugar in a medium saucepan over high heat.

As the berries soften, mash them with a potato masher or fork.

Bring to a boil, then reduce the heat to a simmer. Cook for about 30 minutes, stirring often, until the mixture has reduced by half. Keep a close eye to prevent scorching.

Remove from heat and let the puree cool completely before using.

Preheat your oven to 350°F. Line two 12-cup muffin tins with paper liners (you'll need 18 cups total).

In a medium bowl, whisk together the sifted cake flour, baking powder, and salt.

In a large bowl, beat the butter with an electric mixer until creamy.

Add the sugar and continue beating until the mixture is light and fluffy, about 2 to 3 minutes.

Add the eggs one at a time, beating well after each addition.

Alternate adding the flour mixture and the buttermilk, starting and ending with the flour. Mix just until combined.

Stir in the vanilla extract and the cooled strawberry puree until the batter is uniform.

Divide the batter evenly among the lined cups, filling each about three-quarters full. Bake for 25 to 30 minutes, or until a toothpick inserted into the center comes out clean.

Let the cupcakes cool in the pans for 5 minutes, then transfer them to a wire rack to cool completely.

In a large bowl, beat the room-temperature butter until it is pale and creamy, about 2 minutes.

Add the marshmallow fluff and vanilla extract, and continue beating until smooth.

With the mixer on low speed, gradually add the sifted powdered sugar, one spoonful at a time, until the frosting is thick and fluffy.

Remove the cooled cupcakes from the muffin tins and place them on a serving platter or board.

Fit a piping bag with a large round tip (such as Ateco #808) and fill the bag with the marshmallow buttercream.

Pipe a generous dollop onto the center of each cupcake, then a slightly smaller dollop on top, and finish with a tiny dollop to create the classic ghost shape.

Using tweezers or your fingers, gently press two black sugar pearls onto each ghost for eyes and a few more to form a spooky mouth.

Store the finished cupcakes in a cool, dry place until ready to serve.