1-First Step: Prepare the pan Line an 8×8-inch square baking pan with parchment paper, leaving an overhang on two sides. Lightly coat the pan with cooking spray before adding the parchment. This helps the bars release cleanly later. A parchment sling also makes lifting the finished slab much easier, which matters when the filling is soft.

2-Second Step: Make the cookie crust Place the vanilla wafer cookies and granulated sugar in a food processor. Pulse until fine crumbs form. If you do not have a processor, put the cookies in a resealable bag and crush them with a rolling pin. Drizzle in the melted unsalted butter and pulse again until the crumbs are evenly moistened. The mixture should feel like damp sand and hold together when pressed. Press the crust mixture firmly and evenly into the bottom of the prepared pan. Use the bottom of a measuring cup or glass to pack it down well. A firm crust helps the bars hold their shape when sliced. Freeze the pan for 15 minutes so the base sets before you add the next layer.

3-Third Step: Mix the custard layer Whisk the vanilla instant pudding mix with 2 1/2 cups cold heavy cream until smooth and thick. The cream should be very cold so the mixture firms up nicely. Spread the pudding evenly over the chilled crust. Use an offset spatula or the back of a spoon to smooth the surface. Then refrigerate the pan for at least 10 minutes so the filling firms before the ganache goes on top.

4-Fourth Step: Make the chocolate ganache Place the chopped semi-sweet chocolate in a heatproof bowl. In a small saucepan, bring the 2/3 cup cold heavy cream to a simmer. You do not need a hard boil. As soon as the cream starts to bubble around the edges, pour it over the chocolate. Let it sit for a minute, then whisk until smooth and glossy. For a smooth finish, let the ganache cool for about 3 minutes before pouring. For a slightly swooping top, let it cool for about 5 minutes. This small wait helps control how the topping settles. If the ganache seems too warm, it may melt the custard layer underneath.

5-Fifth Step: Assemble and chill Pour the ganache over the chilled custard layer and spread it to the edges. Gently tilt the pan if needed to help the chocolate reach all corners. Return the pan to the refrigerator and chill until set, at least 2 hours. If you want the cleanest slices, chill a little longer. Patience is the secret here. The bars taste best when each layer is fully chilled and set.

6-Final Step: Slice and serve Lift the slab out of the pan using the parchment overhang. Place it on a cutting board and cut into 12 or 16 pieces, depending on how large you want each bar. Wipe the knife clean between cuts with a cloth for crisp edges. This is especially helpful because the ganache can smudge if the knife gets too warm or sticky. These bars are ready to serve right away, and they look beautiful on a dessert tray. If you are making treats for guests, the neat layers give them a polished, bakery-style look without much effort.