Make the crumble: Preheat oven to 350°F (175°C). In a medium bowl, whisk together the flour, sugar, and salt. Add the cold butter cubes and use your fingers or a pastry blender to cut the butter into the flour until the mixture resembles coarse crumbs.
Bake the crumble: Spread the crumble mixture evenly on a baking sheet. Bake for 15-20 minutes, or until golden brown and crispy. Let cool completely.
Prepare the strawberries: In a medium bowl, combine the sliced strawberries and sugar. Gently toss and let stand for at least 15 minutes (or while you prepare the pudding), allowing the strawberries to release their juices.
Make the pudding: In a large bowl, whisk together the instant vanilla pudding mix and cold milk for 2 minutes, until thickened. In a separate bowl, whip the heavy cream until soft peaks form. Gently fold the whipped cream into the pudding mixture.
Assemble the pudding cups: In individual serving cups or glasses, layer the strawberry shortcake pudding cups in this order:
A spoonful of the shortcake crumble
A layer of the strawberry mixture (including some of the juices)
A layer of the vanilla pudding mixture
Repeat layers, ending with a layer of shortcake crumble on top.
Chill: Cover the pudding cups and refrigerate for at least 2 hours before serving. This allows the flavors to meld and the pudding to set.