Place the peaches, sugar, water, and lemon juice in a spacious bowl and mix well.
Squish the peaches gently with your hands—just enough to get the juices flowing.
Cover with plastic wrap and refrigerate for 6–8 hours.
Remove an hour before serving and bring to room temperature.
Just before assembling, gently add the blackberries.
To assemble the shortcakes, slice the biscuits horizontally and “sandwich” a generous serving of fruit, juices and cream between two biscuit halves. Top with additional cream if desired.
Serve immediately.
Preparation time: 30 minutes with pre-made biscuits, plus several hours downtime