Preheat your oven to 400°F (200°C).
In a large bowl, whisk together the flour, sugar, baking powder, and salt.
Add the chilled, cubed butter into the flour mixture.
Using a pastry cutter, mix until the mixture resembles coarse crumbs.
Pour in the heavy cream and vanilla extract, stirring gently until combined.
If using, fold in the mixed berries carefully.
Turn the dough out onto a floured surface and knead gently.
Pat the dough into a circle about 1 inch thick.
Cut out scones using a round cutter and place them on a baking sheet.
Bake for 20-25 minutes or until golden brown.