Pre heat oven to 425 degrees. Line a rimmed baking sheet with parchment paper. Set aside.
In the bowl of a food processor, pulse together for a few seconds flour, baking powder, baking soda salt, sugar. Add in butter and pulse until mixture resembles coarse sand. Turn mixture out into a large bowl. Make a well and slowly pour in buttermilk. With cold hands, mix the flour mixture and buttermilk until a dough comes together. It should be very shaggy and loose.
Turn out on a lightly floured surface. Work the dough into a rough rectangle. Using a bench scraper, fold the dough into thirds, bringing down the top third into the middle and the bottom third into the center as well- like folding a piece of paper to put in an envelope. Wrap in plastic. Chill for 15 minutes.
While biscuit dough is chilling, combine all ingredients for berry mixture ( all berries through water) in a heavy sauce pan. Bring to a boil then reduce heat to a simmer and let the berries cook, covered for 15 minutes. If mixture becomes too thick, add more water and a bit more lemon juice. You can make this ahead of time and warm up just before assembling the shortcakes.
In the bowl of a stand mixer, beat cream on medium speed for 1 minute, increase speed and add in vanilla and sugar. Beat on high until loose peaks begin to form- about another 30 seconds. Do not over mix. Keep chilled until time to assemble your shortcakes.
Remove the dough from the fridge. On a lightly floured surface, unwrap the biscuit dough. With a floured rolling pin, roll out the dough until it is about 3/4 inch thick. With a glass or a biscuit cutter, cut biscuits into 3"-4" rounds. Place biscuits on prepared baking sheet lined with parchment paper. Brush tops of biscuits with heavy cream and dust with sugar. Bake biscuits for 18-20 minutes or until golden brown and layers are visible. Prior to baking- if the dough gets too warm after rolling out, chill the biscuits for a minute or two.
