PREHEAT oven to 425°F.
MAKE SAUCE: In a food processor, puree 5 cups strawberries with sugar; force through a fine sieve into a bowl. Slice remaining strawberries; stir sliced strawberries and all other berries into puree.
MAKE SHORTCAKES: In a large bowl sift together flour, baking powder, sugar and salt. With a pastry blender or your fingertips blend in butter until mixture resembles coarse meal. Whisk together cream, egg, and vanilla in a separate bowl and, with a fork, stir cream mixture into flour mixture, stirring until mixture just forms soft dough.
ON a lightly floured surface with floured hands, pat dough out into a circle about 1/2 inch thick. With a 3-inch round cutter, cut out 6 rounds. Place rounds on a large baking sheet. Brush tops with milk and sprinkle with sugar and almonds. Bake in middle of oven until golden, about 15 minutes. Cool shortcakes on a rack.
SPLIT shortcakes horizontally and arrange bottom halves on plates. Spoon berries and sauce onto bottom halves. Add shortcake tops and garnish with whipped cream and mint sprigs. Serves 6.