Line your muffin tin with cupcake/muffin liners. Preheat the oven to 350 F (180 C) for conventional oven, 330 F (165 C) for conventional oven
Prepare the cake batter:
Mix whole milk with vinegar and let it sit for 10 minutes. The milk will curdle
If you don't have superfine sugar or caster sugar, you can put regular granulated sugar in a food processor and give it a few blitz to make if finer, but don't turn it into a powdered sugar
In a large mixing bowl, whisk the eggs and sugar vigorously until the sugar melts and the mixture is pale and creamy. You can also use an electric mixer to mix it
Add the mayonnaise and milk mixture and whisk again to combine.
Sift in the dry ingredients (to prevent clumps)
Use a spatula to fold the dry ingredients into the wet. Rotate the bowl as you fold. Just fold until you no longer see dry bits of flour. Don't overmix. The cake batter is medium-thick consistency
Scoop the batter into the prepared pan, 3/4 full. Gently tap the pan on the counter once or twice to pop any large air bubbles. I also use a toothpick to draw some zigzag on the batter to pop any air bubbles trapped inside
Bake in the oven:
Put the pan in the middle rack of the oven. Bake for 15-18 minutes or until a toothpick inserted into the center of the cupcakes come out clean. Do not overbake
Let the cupcakes cool down in the pan for 10 minutes and then remove to a cooling rack and let them cool down completely before frosing the cupcakes
If you use matcha whipped cream:
Mix matcha powder with hot water into a paste and set aside to let it cool down a bit
Make sure the heavy cream is chilled. Chilling the mixing bowl and the whisk in the fridge for at least 15 minutes helps to keep the whipped cream smooth
In a mixing bowl, add heavy cream, vanilla extract, powdered sugar, cornstarch, salt, and the matcha paste. Use an electric mixer fitted with a whisk and stir the mixture a bit to mix so the powdered sugar and cornstarch won't fly when you start the mixer. Start mixing on medium speed until the mixture is firm and can hold its peak, but take care not to overwhip until it turns grainy and separate
Transfer to a large piping bag fitted with star nozzle or whatever shape of nozzle you wish to use
Start piping the whipped cream on top of the cupcakes. Chill the frosted cupcakes in the fridge for at least 2-3 hours or overnight until the whipped cream frosting is set and firm
If using matcha buttercream:
Mix matcha powder with hot water into a paste and set aside to let it cool down completely so it won't melt the butter later
In a mixing bowl, add soft butter (you can easily press on the butter and it leaves indentation but the butter should not be melty), powdered sugar, vanilla extract, matcha paste (make sure it's not hot anymore), and salt. Use an electric mixer fitted with a whisk attachment and start mixing on medium-high speed and whip until the buttercream is fluffy and creamy. Scrape the sides of the bowl halfway if needed
Transfer to a large piping bag fitted with star nozzle or whatever shape of nozzle you wish to use
Start piping the buttercream on top of the cupcakes. Chill the frosted cupcakes in the fridge for at least 1-2 hours or until the buttercream is firm
Storage:
Unfrosted cupcakes can be kept at room temperature, in an air-tight container for 2-3 days. For a longer storage, wrap them in a cling wrap individually and transfer to a freezer bag, push all the air out and seal. They can be kept frozen for one month. Simply remove from the freezer and frost the cupcakes when you need to and then chill the cake in the fridge to let the frosting set as instructed above
Store frosted cupcakes in the fridge, in an air-tight container for 2-3 days. For a longer storage, place the cupcakes on a baking pan and put them in the freezer for about 30 minutes to 1 hour until the frosting is firm to touch and doesn't transfer to your fingers when you touch it. Then transfer the half-frozen cupcakes to freezer-friendly container and they can be kept frozen for one month
When ready to serve, simply thaw at room temperature for 30 minutes to 1 hour, depending on how warm it is where you are.