In a medium bowl, combine the graham cracker crumbs and melted butter. Stir until the crumbs are evenly moistened and look like wet sand.

Press the crumb mixture firmly into the bottom of a 9x13 inch baking dish. Use the bottom of a flat glass to pack it down tightly. Place the dish in the freezer for 10 minutes to set while you prepare the filling.

In a large mixing bowl, beat the softened cream cheese with the powdered sugar and vanilla extract until completely smooth and creamy.

Gently fold in half of the whipped topping using a spatula. Mix until no white streaks remain.

Spread half of the cream cheese mixture evenly over the chilled crust.

Arrange half of the sliced strawberries in a single layer over the cream filling.

Top the strawberries with the remaining cream cheese mixture, spreading it to the edges of the pan.

Spread the remaining whipped topping over the top as the final layer.

Decorate the top with the rest of the sliced strawberries. If using jam, warm it slightly and brush it over the berries for a glossy finish.

Cover the dish loosely and refrigerate for at least 4 hours, though overnight is best for the cleanest slices.