To prepare shortcakes: Preheat oven to 350°F. Line a large baking sheet with parchment paper.
Combine whole-wheat flour, buckwheat flour, 3 tablespoons sugar, baking powder, baking soda and salt in a large bowl. Cut in butter with a pastry blender or two knives until it is the size of peas. Make a well in the mixture and pour in buttermilk and ¼ cup cream (don't wash the measuring cup yet). Stir gently to combine.
Turn the dough out onto a lightly floured surface and pat it into a rectangle about 1 inch thick. Fold the dough over itself and pat into a rectangle about 1 inch thick. Repeat one more time. Cut the dough into 10 equal-size shortcakes. Transfer to the prepared baking sheet. Brush with the dregs of cream left in the measuring cup.
Bake the shortcakes until golden and cooked through, 20 to 25 minutes. Transfer to a wire rack to cool.
To prepare fruit: About 30 minutes before serving, if using vanilla bean, use the tip of a paring knife to scrape the seeds into a large bowl. Add 2 tablespoons sugar and rub the seeds into it with your fingers. Add apricots and/or strawberries (and vanilla extract, if using instead of a bean); gently stir to combine. Let stand at room temperature for 30 minutes. Taste the fruit and add 1 to 2 tablespoons sugar, if desired.
To serve: Beat cream and the remaining 1 tablespoon sugar in a medium bowl with an electric mixer until soft peaks form. Slice each shortcake in half horizontally, top with ¼ cup fruit and some of the cream.
To make ahead: Store shortcakes airtight at room temperature for up to 1 day.
Serving size: 1 shortcake with ¼ cup fruit & 3 Tbsp. whipped cream
301 calories;18 g fat(11 g sat); 3 g fiber; 33 g carbohydrates; 5 g protein; 14 mcg folate; 57 mg cholesterol; 15 g sugars; 8 g added sugars; 1,646 IU vitamin A; 6 mg vitamin C; 143 mg calcium; 2 mg iron; 297 mg sodium; 284 mg potassium
Vitamin A (33% daily value)
Carbohydrate Servings: 2
Exchanges: 1 starch, ½ fruit, ½ other carbohydrate, 3½ fat