1-First Step: Prepare the pan Line an 8×8-inch square baking pan with parchment paper, leaving some overhang on the sides so you can lift the bars out later. Coat the parchment lightly with cooking spray. This step makes slicing and serving much easier at the end.

2-Second Step: Make the cookie crust Place the vanilla wafer cookies and granulated sugar in a food processor. Process until fine crumbs form. If you do not have a food processor, put the cookies in a sturdy bag and crush them with a rolling pin until they are very fine. Transfer the crumbs to a bowl, then mix in the melted unsalted butter until everything looks evenly moistened. Press the crumb mixture firmly into the prepared pan. Use the bottom of a measuring cup or your fingers to make an even layer. A tight, even crust helps the bars cut neatly later. Freeze the crust for 15 minutes so it firms up before the filling goes on.

3-Third Step: Mix the custard layer In a medium bowl, whisk the 2 boxes of vanilla instant pudding mix with the 2.5 cups cold heavy cream. Keep whisking until the mixture is smooth and thick. It should look like a soft custard and hold its shape when spread. Spread the pudding mixture evenly over the chilled crust. Work slowly so you do not pull up the crust underneath. Once the filling is spread, refrigerate the pan for at least 10 minutes. This short chill helps the layer set enough to support the ganache.

4-Fourth Step: Make the chocolate ganache Place the chopped semi-sweet chocolate in a heat-safe bowl. In a small saucepan, heat the 2/3 cup cold heavy cream just until it reaches a simmer. Do not let it boil hard. Pour the hot cream over the chocolate and let it sit for 1 minute so the chocolate can soften. Whisk the mixture until it becomes smooth and glossy. If a few chocolate pieces remain, keep stirring gently until they melt. Let the ganache cool slightly before pouring it over the pudding layer. For a smooth pour, cool it for about 3 minutes. If you want swoops or swirls, wait about 5 minutes so it thickens a bit more.

5-Fifth Step: Finish the bars Pour the ganache over the chilled custard layer and spread it evenly with a spatula. If you want a pretty pattern, gently swirl the top with the back of a spoon or a butter knife. Keep the movement light so you do not mix the layers together. Refrigerate the pan for at least 2 hours, or until the bars are fully set. This chill time is what gives the dessert clean slices and that firm, bakery-style finish. If you try to cut them too soon, the layers may slide.

6-Final Step: Slice and serve Use the parchment overhang to lift the bars out of the pan. Place them on a cutting board and cut into 12 to 16 pieces, depending on how large you want each serving. Wipe the knife between cuts for the cleanest edges.