In a bowl, combine sliced strawberries and granulated sugar. Toss to coat and let sit for 15 minutes to macerate.

Preheat the oven to 350°F (175°C).

In a mixing bowl, cream together the softened butter and sugar until light and fluffy.

Add the egg and vanilla extract, mixing well.

In another bowl, whisk together the flour and baking powder.

Gradually add the dry ingredients to the wet mixture, alternating with milk, and mix until just combined.

Spoon the batter into a greased muffin tin, filling each cup about 2/3 full.

Bake for 12-15 minutes or until a toothpick inserted in the center comes out clean.

Allow to cool completely.

In a mixing bowl, whip the heavy cream, powdered sugar, and vanilla extract until soft peaks form.

Once the cake is cool, cut each muffin in half horizontally.

Layer the bottom half of the cake with macerated strawberries, followed by a generous dollop of whipped cream.

Top with the other half of the cake and repeat the layering with more strawberries and whipped cream.

Serve immediately or chill until ready to serve.