In a large bowl, whisk flour, baking powder, salt, and sugar to blend. Cut in butter with a pastry cutter or forks until butter is about the size of peas. Crack egg into a measuring cup and add milk to come to the 3/4 cup line. Whisk, then pour over flour mixture. Use a rubber spatula to mix gently until the flour is just moistened. The mixture should be very lumpy.
Spoon a tablespoon or two of the batter into the cups of a mini muffin pan. Flatten the tops a bit with the back of a spoon or fingertips.
Bake 10 minutes, until golden. Let cool slightly in pan then remove to a wire rack and cool completely.
Meanwhile, beat the cream, sugar, and vanilla in a medium bowl until soft peaks form.
Right before serving, top each mini shortcake with a dollop of whipped cream and strawberry.