Take the ice cream out of the freezer and let it sit on the counter for 15–20 minutes – just until it is spreadable but not soupy. Do not microwave it. Do not leave it out for an hour. Trust me on this one.
Make the compote: In a small saucepan, combine half the strawberries (diced), 1/4 cup sugar, and lemon juice. Cook over medium heat, stirring occasionally, until the berries break down and the mixture thickens slightly – about 8–10 minutes. Remove from heat and let cool completely.
Toast the shortcake twice: Preheat the oven to 350°F. Crumble the shortcake biscuits into uneven pieces (think: gravel, not dust). Spread on a parchment-lined baking sheet and bake for 8 minutes. Let cool, then crumble a bit more. Bake again for 5 minutes until deep golden. Let cool completely.
Brush with the barrier: Melt the white chocolate in 20-second bursts in the microwave (or over a double boiler). Use a pastry brush to lightly coat the bottom and halfway up the sides of the springform pan with a thin layer – this helps the cake release cleanly. Then toss the cooled shortcake crumbs with the remaining melted chocolate until every piece is coated. Press half the crumbs firmly into the bottom of the pan. Reserve the rest.
Layer the ice cream: Spread half the softened ice cream over the crumb layer, pressing gently with a spatula. Spoon the cooled strawberry compote over the ice cream in dollops and swirl with a knife. Freeze for 15 minutes to firm up slightly.
Add the remaining crumbs and ice cream: Sprinkle the reserved shortcake crumbs over the compote layer. Spread the remaining ice cream on top, smoothing into an even layer. Freeze for at least 4 hours, or overnight.
Whip the cream: When ready to serve, beat the heavy cream, vanilla, and remaining 1 tablespoon sugar until soft peaks form. Do not overbeat – you want it billowy, not stiff.
Assemble and serve: Run a hot knife around the edge of the pan, release the springform, and transfer the cake to a serving plate. Pile the whipped cream on top and garnish with the remaining fresh strawberries. Slice with a warm, dry knife, wiping between cuts.