Preheat the oven to 375°F (190°C). Line a muffin tin with 6 paper liners.
In a large bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, and salt.
In a separate bowl, whisk together the buttermilk, melted butter, egg, and 1 teaspoon vanilla extract until combined.
Pour the wet ingredients into the dry ingredients and gently fold together until just combined. Do not overmix.
Fold in 1 cup fresh blueberries gently into the batter.
Divide the batter evenly among the 6 muffin cups, filling each about 3/4 full.
Bake for 18 to 20 minutes, or until a toothpick inserted into the center comes out clean.
Remove muffins from the oven and let cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.
While the muffins cool, prepare the whipped cream. In a chilled mixing bowl, beat the heavy whipping cream, powdered sugar, and 1/2 teaspoon vanilla extract on medium-high speed until stiff peaks form.
To assemble the shortcakes, slice each blueberry muffin in half horizontally.
Place the bottom half of a muffin on a serving plate, spoon a generous amount of whipped cream over it, and top with a few fresh blueberries.
Place the muffin top over the blueberries and add an additional dollop of whipped cream and a few more fresh blueberries on top for garnish.
Repeat with the remaining muffins and serve immediately.