Photo: David Munns
Preheat the oven to 180ºC / 350ºF / gas 4. Line a 15-hole muffin pan with paper cases.
Put the flour, salt, and baking powder into a medium bowl, then add the sugar. Add the cubes of softened butter, dotting them evenly into the flour mixture. Blend with an electric mixer, starting on slow speed and working up to medium until evenly incorporated. Add the eggs one at a time, beating to combine.
Combine the milk and vanilla extract in a separate jug, and then add to the batter in three parts, beating well after each addition.
Using an ice cream scoop, spoon the batter into the paper cases, filling them three-quarters full. Bake for 15 minutes, or until a toothpick inserted into the centre comes out clean.
Cool in the muffin pan for a few minutes, then transfer to a wire rack to cool completely before decorating.
You will need a small saucepan and a heatproof bowl that will sit neatly on top of it (or use a double boiler if you have one). Pour a few cups of water into the pan and bring to the boil. The water should not touch the base of the bowl.
Whisk the egg whites, sugar, cream of tartar, and salt in the bowl using an electric mixer, then place the bowl above the boiling water and continue whisking until the mixture is hot to the touch and all the sugar has dissolved—about 1–2 minutes.
Remove from the heat and using the mixer on medium-high speed beat until the eggs form a cool stiff meringue – about 5 minutes or until hard peaks have formed.
Secure a marshmallow vertically in the centre of a cake using a tiny dab of the meringue, and use a spoon to heap frosting on top of each cupcake to make a ghost shape you like. Smooth the edges with the back of the spoon.
Use black fondant or chocolate chips to create “eyes” with a suitably menacing expression.