Strawberry shortcake is a quintessential springtime dessert in America, and it's difficult to improve on the original. Here we've added rhubarb (long considered a perfect partner for strawberries), fresh mint, and hint of orange for a twist on the classic version.
These shortcakes are light, melt-in-your-mouth biscuits rather than those spongy supermarket cakes. Adding crystallized ginger gives them a bit of texture and flavor, but this is strictly optional. The shortcakes are best when baked within an hour or two of serving, but the fruit filling can be assembled a day in advance.
Position a rack in the middle of the oven and preheat to 425 degrees F.
Make the shortcakes: In a large bowl, whisk together the flour, sugar, baking powder, baking soda, salt, ginger, cardamom, crystallized ginger (if using), and orange zest. Add the butter and rub it in with your fingertips until the mixture resembles coarse meal.
Add the buttermilk slowly, and toss the mixture with a fork to combine. Don't overwork the dough or the shortcakes will be tough.
Turn the dough out of the bowl onto a counter or board. Divide into 4 pieces and gently pat each piece into a 3-inch round (again, don't overwork the dough). Transfer to a baking sheet, spacing the dough rounds evenly so they don't touch.
Bake until a toothpick inserted into the center of one of the shortcakes comes out dry, 12 to 15 minutes. Remove from the oven and let cool 5 minutes on the baking sheet. Transfer the biscuits to a wire rack and finish cooling.
Make the fruit topping: Place the sugar and orange juice in a medium saucepan and bring to a boil over high heat. Stir to dissolve the sugar. Reduce heat to medium and add the rhubarb. Cook, stirring occasionally, until the rhubarb is just tender, about 5 minutes. Don't overcook or let the mixture boil, or the rhubarb will dissolve into a purée.
Roughly mash one cup of the strawberries. Remove the pan from the heat and add the quartered and mashed strawberries. Let cool to room temperature, then add the Grand Marnier and mint. Transfer to a bowl and refrigerate, covered, for at least one hour or overnight.
To assemble: Just before serving, whip the cream with the sugar until soft peaks form. Add the Grand Marnier and continue beating until the cream is stiff.
Split the shortcakes horizontally with a fork, and place the bottoms on 4 plates. Spoon the fruit filling over the biscuits, and top with a generous dollop of whipped cream. Arrange the top halves of the shortcakes over the fruit and serve immediately.