Biscuits: Sift the flour, sugar, baking powder, and salt into a large bowl.
Add the butter and rub it in with your fingertips until the mixture resembles a coarse meal.
Gradually add the buttermilk, tossing with a fork until large moist clumps form.
Gather the dought into a ball. Divide it into 4 pieces. Shape each piece into a 3-inch round. Transfer the rounds to a baking sheet, spacing them evenly.
Bake the biscuits until a tester inserted into the centre comes out dry (about 20 minutes) - the biscuits will be pale. Transfer the biscuits to a rack and cool until they are lukewarm. (The biscuits can be prepared 6 hours ahead; cool, wrap tightly in aluminum foil, and store at room temperature; before serving, reheat the biscuits in a 350 F oven for 5 minutes).
Strawberry Filling: Combine the strawberries, 1/2 cup sugar, and raspberry preserves in a large bowl. Toss to coat. Let the strawberries stand for about one hour until a syrup forms, tossing occasionally.
Whipped Cream: Beat the chilled whipping cream, vanilla extract, and remaining 3 tbsp of sugar in another large bowl until stiff peaks form. (The whipped cream can be made 6 hours ahead; cover separately and chill).
Assemble: Cut the buttermilk biscuits in half. Place each biscuit bottom in a shallow bowl. Top each generously with strawberries and whipped cream. Cover the fruit and cream with the biscuit tops. Dust the biscuits with powdered sugar and serve.