For the macerated strawberries: Combine the strawberries and sugar in a medium bowl. Toss to combine. Cover with plastic wrap and refrigerate 1 to 2 hours.
For the shortcakes: Preheat the oven to 400 degrees F.
In a medium bowl, whisk together the flour, baking powder, sugar, salt, and pepper if using. Using a bowl scraper or your fingers, work in the butter until the mixture resembles a coarse meal (using your fingers will create a more cake-like texture). Add the rhubarb and toss to coat; make a well in the center. Combine the 1/2 cup milk, the cream and the vanilla, and pour this into the well. Mix just until combined.
Turn the dough out onto a floured surface and knead 5 or 6 times, then roll into a 3/4-inch-thick disc. Cut out rounds using a 3-inch biscuit cutter; make sure you don't twist the cutter, otherwise you'll squish the sides and the shortcakes won't rise. Knead the scraps together, re-roll and cut out rounds until all the dough has been used.
Place the rounds, bottom-side up, on a parchment-lined baking sheet. Brush each with milk and sprinkle with turbinado sugar. Bake until the tops are golden brown, about 25 minutes. Let cool completely on the baking sheet.
With a serrated knife, cut the shortcakes in half horizontally and place on a serving plate. Top the bottom halves with macerated strawberries and whipped cream, and cover with the top halves. Serve immediately.