Step 1

Hull 1 pound of the fresh strawberries, and cut in half lengthwise; set aside. Hull and chop strawberries from remaining 1 pound berries to measure 1 cup; set aside. (Reserve remaining whole berries for another use.)

Step 2

Preheat oven to 400°F. Coat a 13- x 9-inch rimmed baking sheet with cooking spray. Whisk together self-rising flour, all-purpose flour, salt, and ½ cup of the granulated sugar in a large bowl. Cut cold butter cubes into flour mixture until butter pieces are evenly coated and pea size. Gently fold in buttermilk, lemon zest, ⅔ cup of the whipping cream, and 1 teaspoon of the vanilla until mixture just comes together but is still lumpy. Gently fold in reserved chopped strawberries.

Step 3

Using a ¼-cup measuring cup dusted with all-purpose flour to prevent sticking, scoop slightly rounded dough mounds onto prepared baking sheet in 3 rows of 6 side-by-side mounds, continuing to flour scoop after each mound to prevent sticking. Brush dough mounds evenly with melted butter, and sprinkle with sanding sugar. Bake in preheated oven until golden brown, 28 to 32 minutes. Transfer baking sheet with shortcake to a wire rack, and cool 10 minutes. Transfer shortcake to wire rack; cool completely, about 1 hour.

Step 4

Meanwhile, stir together halved strawberries and remaining ¼ cup granulated sugar in a medium bowl, and let stand until berries start to release their juices, 10 to 15 minutes.

Step 5

Gently stir together mascarpone cheese, powdered sugar, and remaining 2 teaspoons vanilla in a separate medium bowl until just combined. Pour remaining 1 cup whipping cream into a separate large bowl, and beat with an electric mixer fitted with a whisk attachment on high speed until stiff peaks form, 2 to 3 minutes. Gently fold whipped cream into mascarpone mixture until just combined.

Step 6

Spread whipped cream-mascarpone mixture over top of cooled shortcake, leaving edges exposed. Top with strawberry mixture and any accumulated juices. Slice evenly into 12 pieces, and serve immediately.