For best results I recommend chilling your butter in the freezer for about 15 minutes before beginning. Cold butter yields light, buttery shortcakes. A chilled metal bowl will also make whipping your cream easier and faster, so while it is not mandatory it would be helpful to place one in the freezer at this point that you can use it for your whipped cream.
Start by preparing your strawberries. Place sliced strawberries in a medium sized bowl and add 3 tablespoons of sugar. Stir well and set aside so they can get nice and juicy while you prepare your shortcakes.
Preheat oven to 425F (220C) and line a baking sheet with parchment paper. Set aside.
In a large bowl combine flour, sugar, baking powder, and salt and whisk to combine.
Use a box grater² to grate cold butter into the dry ingredients. Stir until mixture resembles coarse crumbs. Add heavy cream and milk and use a spoon or spatula to stir until ingredients are combined. Don't over-work the dough, but stir until it begins to cling together.
Transfer shortcake dough to a floured surface and work the dough together with your hands, adding more flour as needed if the dough is sticky.
Once the dough is a cohesive ball, fold it in half over itself and use your hands to gently flatten the layers. Rotate dough 90 degrees, then fold in half again. Repeat this step 5-6 times, taking care to not overwork the dough (see video below the recipe for a visual if needed). This is laminating the dough and gives you those flaky layers!
Using your hands, gently flatten the dough to 1" thick. Lightly dust a 2 3/4" round biscuit cutter³¾ with flour, and press the biscuit cutter straight down (don't twist) to cut out shortcakes. Place shortcakes on prepared baking sheet, less than 1/2" apart.
Once you have cut as many shortcakes as possible out of the dough, gently re-work the dough to get out another shortcake or two until you have at least 6 (sometimes I'm able to get 7. Brush with additional heavy cream and sprinkle generously with coarse sugar (if you don't have coarse sugar, regular granulated will also work just fine).
Bake on 425F (220C) for 14-15 minutes or until tops and bottoms of shortcakes are beginning to just turn lightly golden brown.
Prepare whipped cream while shortcakes cool.
Combine heavy cream, powdered sugar, and vanilla extract in a large bowl (if you chilled a bowl before starting, use that now).
Using an electric mixer, beat ingredients on low speed, gradually increasing speed to high, and beat until stiff peaks form. Don't over-beat, but don't stop beating until cream has reached a billowy Cool-Whip consistency.
To Assemble Shortcakes
Slice cooled shortcakes in half and place the bottom half cut-side up on a plate.
Stir your strawberries once more (they should be nice and juicy by now) and top one shortcake half generously with your prepared strawberries, and then with a dollop of homemade whipped cream.
Top the whipped cream with the top half of your shortcake, and then top with additional whipped cream and finally additional strawberries. Serve immediately after assembling.
¹I like to use a blend of heavy cream and milk for the most tender shortcakes, but in a pinch you can leave out the cream and increase the milk to 3/4 cup (2% milk or buttermilk would also work).²If you don't have a box grater, use a pastry cutter to cut the butter into the flour. ³If you don't have a biscuit cutter, use the rim of a clean glass or just use a knife and cut the shortcakes into squares. The important thing is you press straight down when cutting and don't twist or saw, which will keep your biscuits from rising properly.