1. Prepare the pan by lightly greasing a 9×13 inch dish or lining it with parchment paper so you can lift the dessert out easily for slicing.

2. Make the crust by combining the shortbread cookie crumbs and melted butter in a bowl until the mixture resembles damp sand and holds together when pressed.

3. Press the crumb mixture firmly and evenly into the bottom of the prepared dish, packing it down well with the bottom of a measuring cup. Place the pan in the refrigerator or freezer to chill while you make the filling.

4. Beat the cream cheese in a large mixing bowl until smooth and creamy, scraping down the sides of the bowl as needed so there are no lumps.

5. Add the powdered sugar and vanilla extract to the cream cheese and beat again until the mixture is fluffy and well combined.

6. In a separate bowl whip the cold heavy cream to soft peaks, or if using whipped topping, gently fold it into the cream cheese mixture until the filling is light and airy.

7. Spread half of the cream cheese filling over the chilled crust, smoothing it into an even layer all the way to the edges of the pan.

8. Arrange an even layer of sliced strawberries over the filling so that every bite will have plenty of fruit.

9. Drizzle the strawberry jam or strawberry sauce over the strawberries, using the back of a spoon to lightly spread it without disturbing the berries too much.

10. Spoon the remaining cream cheese filling over the strawberry layer and carefully spread it out to completely cover the berries.

11. In a small bowl stir together the brown sugar and extra shortbread cookie crumbs, then sprinkle this mixture evenly over the top of the dessert.

12. Add extra sliced or whole strawberries on top for decoration, gently pressing them into the creamy layer so they stay in place.

13. Cover the pan tightly with plastic wrap or a lid and refrigerate for at least 4 hours or until the dessert is fully chilled and set; overnight chilling gives the cleanest slices.

14. When ready to serve, use a sharp knife to cut the dessert into squares, wiping the knife between cuts for neat layers, and plate each slice with extra strawberry sauce if desired.