Preheat oven to 400 degrees F. Lightly grease a baking sheet; set aside. In a medium bowl combine flour, the 1/4 cup sugar, the baking powder, salt, and baking soda.
Here's the important part: Cut the cold butter into small cubes. Use a pastry blender or two knives (hold the blades next to each other, pulling in opposite directions) to cut in the butter into pea-size pieces.
Make a well in center of flour mixture. In a small bowl combine egg, sour cream, and milk. Add to flour mixture all at once, stirring with a fork just until moistened. Be careful not to overstir.
"Drop" dough into eight mounds on the prepared baking sheet by scooping it with one spoon and using another spoon to push it off. Bake in oven for 12 to 15 minutes or until golden. Transfer to a wire rack and let cool.
Slice strawberries for the filling and garnish. (Mix it up by using other types of berries.) Combine 4 cups of the strawberries and the 3 tablespoons sugar. If desired, use a potato masher to mash berries slightly; set aside.
To serve, halve cooled shortcakes crosswise. A serrated knife works best, because it won't compact the crumb of the shortcake. Spoon strawberry mixture and Sweetened Whipped Cream over shortcake bottoms. Replace shortcake tops. Top with remaining sliced strawberries.