Preheat the oven to 400°F. Line a baking sheet with parchment paper.
In a large bowl, whisk together flour, sugar, baking powder, and salt.
Grate the frozen butter and use your hands to work it into the flour mixture until it resembles a coarse meal with pea-sized pieces.
In a separate bowl, whisk buttermilk, egg, and vanilla extract.
Gently fold in the well-drained cottage cheese and berry jam into the wet ingredients.
Pour wet ingredients over dry and stir lightly with a spatula just until combined. The dough should be soft but not sticky; add more flour if too wet or more buttermilk if dry.
Turn dough out onto a lightly floured surface and shape into a 7-8 inch disk about 1 inch thick. Cut into 8 wedges.
Freeze wedges for 15 minutes to chill butter.
Brush tops lightly with buttermilk, sprinkle with coarse sugar if desired.
Bake for 20-25 minutes or until scones are golden brown and cooked through. Cool on a wire rack before serving