Strawberry Rhubarb Sauce
In a medium saucepan over medium heat, combine granulated sugar, water, and cardamom pods. Bring the mixture to a gentle simmer before adding the rhubarb. Allow the rhubarb to cook for approximately five minutes, stirring occasionally, until it softens and begins to break down. Remove from heat and transfer the sauce to a bowl to cool. Once cooled, fold in the sliced strawberries.
Sugar Biscuits
Preheat the oven to 450°F and line a baking sheet with parchment paper or a silicone baking mat.
In a large mixing bowl, whisk together the flour, baking powder, baking soda, and salt. Distribute the cold butter over the dry ingredients, then use a pastry cutter, fork, or your hands to incorporate it until the mixture resembles coarse crumbs. Gradually pour in the buttermilk, stirring gently until just combined.
Lightly flour a clean surface and place the dough on top. Pat the dough into a 10x12-inch rectangle, about ¾-inch thick. Using a 3-inch round cutter, stamp out biscuits, reshaping scraps as needed. Arrange them on the prepared baking sheet, brush the tops with heavy cream, and sprinkle with granulated sugar.
Bake for 10–12 minutes or until the biscuits turn golden brown. Remove from the oven and allow them to cool slightly before serving.
Vanilla Whipped Cream
In a large mixing bowl or the bowl of a stand mixer fitted with the whisk attachment, beat the heavy whipping cream on high speed for two minutes. Reduce the speed to low and add the powdered sugar and vanilla. Return to high speed and continue beating until stiff peaks form, approximately one minute.
Strawberry Rhubarb Shortcake Assembly
Slice the sugar biscuits in half horizontally. Spoon a generous portion of the strawberry rhubarb sauce over the bottom halves, then add a dollop of vanilla whipped cream. Place the top halves of the biscuits over the filling and serve immediately. Enjoy!