Preheat oven to 425 degrees. Have ready a parchment lined baking sheet.
Whisk together the sour cream and JUST HALF OF the milk.
Mix the flour, sugar, baking powder, baking soda, and salt in a large bowl. Grate the cold butter into the flour mixture and toss to distribute it evenly. If using lemon zest, add that too.
Add the sour cream/milk mixture to the dry ingredients along with the vanilla and stir until it just comes together. Add remaining milk, plus more if needed to make a soft dough. Transfer the dough to a pastry mat. If dough is very sticky, flour the mat. If it is dry, you won't need flour yet. Press into a rectangle, then fold the dough into thirds. Press down again and fold into thirds.
Press down into a large rectangle (about 1/2 inch thick). Dot rectangle with berries and cubes of cream cheese, then carefully fold the dough over on itself, being careful not to squash the berries. Use flour as needed to prevent sticking.
Using a 2 1/2 inch round cutter, cut as many scones as you can. Gently shape the scraps into flat slab and cut remaining circles. You should get about 5,
Arrange scones on a parchment lined baking sheet. Brush with heavy cream and sprinkle with some more sugar or coarse sugar if you have it.
Bake the scones at 425 for about 10 minutes, then reduce heat to 375 and continue baking for another 10 to 15 minutes or until scones are golden and cooked through. If you used unfrozen berries or a different fruit, the scones might be done sooner.
Let the scones cool before serving. The texture actually improves as the scones cool.