Strawberry Icebox Shortcake

3 cups hulled and roughly chopped fresh strawberries (from 1 lb. strawberries), plus hulled and sliced fresh strawberries,

for decorating ½ cup granulated sugar Nonstick cooking spray

4 cups heavy whipping cream

½ cup confectioners› sugar

2 ½ teaspoons pure vanilla extract

5 cups shortbread cookies (such as Lorna Doone) from two 10-oz. pkgs.

Pulse chopped strawberries and granulated sugar in a blender or a food processor until berries are finely chopped but still chunky, about 5 pulses. Transfer mixture to a small bowl. Refrigerate until ready to use. Coat a 9x13-in. baking dish with cooking spray; set aside. Beat cream, confectioners’ sugar, and vanilla in the bowl of a stand mixer fitted with a whisk attachment on medium speed until starting to thicken, about 1 minute. Raise mixer speed to medium-high; beat until medium-to-stiff peaks form, 3 to 4 minutes. Add pulsed strawberry mixture; beat on medium speed until just combined, about 10 seconds. Spread a third (about 3 cups) of the whipped-cream mixture in the bottom of the prepared baking dish. Arrange half the cookies in a single layer (all facing up) on top of cream, breaking cookies as needed to fill any gaps and create a solid layer. Repeat layers with one third of the whipped-cream mixture and remaining cookies. Spread top with remaining whipped-cream mixture. Wrap baking dish in plastic wrap. Refrigerate until set, at least 6 hours or up to 12 hours. Unwrap baking dish. Decorate cake with sliced strawberries. Cake may be lightly wrapped in plastic wrap and stored in refrigerator for up to 3 days.