In a saucepan, combine strawberries and sugar.

Cook on medium heat, covered, stirring occasionally, until the strawberries become soft and mushy.

In a small bowl, mix cornflour with water to make a slurry.

Reduce heat to low and add the slurry to the strawberry mixture.

Stir continuously until the mixture thickens slightly.

Turn off the heat and strain the mixture through a sieve.

Press with a spoon to extract as much liquid as possible.

Reserve the thick residue for the buttercream.

Cover the strained compote and let it cool completely.

Preheat oven to 180°C / 350°F.

Line a cupcake tray with liners.

In a bowl, whisk flour, baking powder, baking soda, salt, and cornflour. Set aside.

In another bowl, mix milk and oil. Set aside.

In a large bowl, beat butter and sugar until pale and creamy.

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

Add vanilla and mix.

Add dry ingredients and milk mixture alternately, starting and ending with dry ingredients.

Mix only until combined. Do not overmix.

Fold in chopped strawberries gently.

Fill liners about ⅔ full.

Bake for 20–22 minutes or until a toothpick comes out with a few crumbs.

Cool 5 minutes in pan, then transfer to rack to cool completely.

Add egg whites and sugar to a heat-safe bowl.

Place bowl over a pot with simmering water, making sure the bowl does not touch the water.

Stir constantly until sugar dissolves and mixture reaches about 65–70°C.

Remove from heat.

Beat with mixer until stiff, glossy peaks form.

Add softened butter little by little while beating.

Continue beating until smooth and creamy.

Add reserved strawberry residue.

Add food color if desired.

Beat until fluffy.

Use a knife or melon baller to remove the center of each cupcake halfway deep.

Fill the center with cooled strawberry compote.

Pipe buttercream on top.

Make a small depression using the back of a spoon.

Fill with more compote.

Garnish with mint leaves if desired.

Serve at room temperature.