Preheat the oven to 350°F (177°C). Line a 12-cup muffin pan with cupcake liners. This recipe yields about 15 cupcakes, so line a second muffin pan with 3 cupcake liners, or bake in batches.

In a large bowl, whisk the flour, baking powder, baking soda, and salt together. Set aside.

In a medium bowl, whisk the melted butter and sugar together. Mixture will be gritty. Whisk in the egg whites, sour cream, milk, and vanilla extract until combined.

Pour the wet ingredients into the dry ingredients and whisk until the batter is completely combined. Batter should be creamy and mostly smooth; a few small lumps are OK. With a spatula, gently fold in the blueberries.

Pour/spoon the batter into the liners, filling only 2/3 full to avoid spilling over the sides. You should have enough batter for 15 cupcakes.

Bake for 20–22 minutes, or until a toothpick inserted in the center comes out clean.

Remove cupcakes from the oven and allow them to cool in the pan for 10 minutes, and then transfer to a wire rack to cool completely. Cupcakes must be completely cooled before topping.

In a large bowl using a hand mixer or a stand mixer fitted with a whisk attachment, whip the heavy cream on medium-high speed until stiff peaks form, about 3–4 minutes. If you accidentally over-whip the cream, and it looks curdled and heavy, pour in a little bit more cold heavy cream, and fold it in gently by hand with a spatula until it smooths out. Transfer the whipped cream to a medium bowl.

In the same bowl used for the whipped cream (no need to wash it), beat the cream cheese on medium-high speed until smooth and creamy. Scrape down the sides of the bowl as needed. Add the confectioners’ sugar, lemon zest, lemon juice, and vanilla extract and beat until smooth, about 2 minutes. Add the whipped cream to the cream cheese mixture and gently fold together with a spatula just until combined. Do not overmix.

Frost cooled cupcakes. You can use a piping bag and tip to pipe the frosting on, or spread it on with an icing spatula or knife. I used piping tip Ateco 808. Garnish cupcakes with fresh blueberries and/or mint, if desired.

Serve immediately or store in the refrigerator until ready to serve. Cover and store leftover cupcakes in the refrigerator for up to 5 days. I recommend a cupcake carrier for storing and transporting decorated cupcakes.