For the shortcakes:
Preheat the oven to 400 degrees. Place the flour, baking powder, sugar, salt, and butter in a food processor. Pulse for 5 seconds at a time until the mixture resembles coarse sand.
Transfer the mixture to a large bowl. Add 1 egg, cream and lemon zest; mixing the until a dough is formed.
Place the dough on a floured surface and form it into a ball. Flatten the dough until you end up with a disc that's approximately 1 inch tall.
Cut the disc diagonally to form 6 triangles. Beat the second egg in a small bowl and brush the tops of the shortcakes with the egg. Sprinkle the coarse sugar evenly over the tops (this is optional but it looks really pretty!).
Bake on a baking sheet lined with parchment paper for 15-18 minutes or until golden brown. Let cool for 5 minutes then remove the shortcakes from the baking sheet and cool on a wire rack. While the shortcakes are in the oven, prepare the blueberry sauce and whipped cream.
For the blueberry sauce:
Combine 2 cups of the blueberries, sugar and lemon juice in a pot. Place the pot over high heat, boil for 3-4 minutes or until blueberries have just started to break down. Mix together the cornstarch with 1 teaspoon cold water. Add the cornstarch mixture to the blueberries and boil for 1 additional minute until sauce thickens slightly. Remove from heat and stir in the remaining cup of blueberries; set aside to cool.
For the whipped cream:
Place 1/2 cup heavy cream in the bowl of a mixer; beat with a whisk attachment until stiff peaks form; add 2 tablespoons of sugar and beat for an additional 30 seconds to combine.
Using a serrated knife, slice the shortcakes in half. Place 1/3 cup of blueberry sauce onto the bottom of each shortcake and top with 1/2 cup of ice cream. Add the top piece of the shortcake.
Place a dollop of whipped cream on top and serve, garnished with mint sprigs and lemon slices if desired.