- Preheat the oven to 350 degrees. Place one rack in the middle. Line two pans of 1-dozen-each muffin tins (1 cup size) with paper liners or grease well with soft butter.
- In a medium bowl, combine the dry ingredients (flour, baking powder and salt) and mix well to break up any lumps. Set aside.
- Place butter in the bowl of a stand mixer fitted with the paddle attachment (ordinary beaters work too, but can be messier) and beat on medium-high speed until very light in color, about 3 minutes.
- Add sugar and vanilla seeds (if you're using extract instead, wait and add it later), and continue beating until it is light and airy, about 3 minutes.
- Scrape down the paddle and the sides of the bowl. Turn the mixer to medium speed and, one at a time, add the egg whites, beating well to incorporate after each addition. Then add the eggs one at a time, again beating well after each addition.
- Add the milk (add the vanilla extract here, if you are using it) and mix until combined. It will look lumpy. Scrape down the sides of the bowl. Reduce the speed to low, add the mixed dry ingredients and fold together until just combined, about 15 seconds.
- Fill the muffin tin wells each about halfway (4 ounces each). If a well or two does not get filled, fill it with ½ cup water instead. Bake in preheated oven until the cupcakes are golden brown on top and a toothpick inserted into the center comes out clean, roughly 15 to 18 minutes.
- Set the pans on a wire rack and let cool for 5 minutes. Remove the cupcakes from the pans and let cool completely before topping.
- While the cupcakes are cooling, put the cream in a mixing bowl with a wire whip attachment (or whip by hand with a whisk). Stir in the sugar and vanilla, then whip to stiff peaks, but not dry.
- Immediately before serving, top cooled cupcakes with a dollop of whipped cream and fruit.
* To scrape vanilla beans, use a sharp paring knife and carefully split the bean in two, lengthwise. Using the dull edge of the knife, and sometimes the point, gently scrape out the very small seeds from the pod. Reserve the seeds, discard the pod.
To preserve leftover vanilla beans, store them in sugar in an airtight container. The beans will be preserved for months at a time, and the sugar will take on the vanilla flavor.