1-First Step: Prepare the pan and crumb crust Start by lightly coating an 8-inch or 9-inch square baking pan with cooking spray. This helps the bars release cleanly later. Then place the vanilla wafer cookies in a food processor and pulse until they become fine crumbs. If you do not have a food processor, place the cookies in a sealed bag and crush them with a rolling pin. Transfer the crumbs to a medium bowl, then add the granulated sugar and melted unsalted butter. Stir until all the crumbs look evenly coated and feel like damp sand. Press the mixture firmly into the bottom of the prepared pan. Use the bottom of a measuring cup or your fingers to make the crust even and compact.

2-Second Step: Chill the crust Place the pan in the refrigerator while you prepare the filling. A short chill helps the crust firm up so it can hold the custard layer without getting soggy. Even 10 to 15 minutes makes a difference.

3-Third Step: Make the creamy custard layer In a large bowl, whisk the two boxes of vanilla instant pudding mix with the cold heavy cream. Whisk for a few minutes until the mixture thickens. You want it smooth, creamy, and fluffy. If you prefer a softer texture, stop whisking as soon as it reaches a thick pudding consistency. For a more mousse-like filling, whisk a little longer until it gets lighter. Once the pudding mixture thickens, spread it over the chilled crust. Use a spatula to make an even layer from edge to edge. Try to keep the surface smooth so the ganache sits nicely on top.

4-Fourth Step: Make the chocolate ganache Place the chopped semi-sweet chocolate or chocolate chips in a heat-safe bowl. Heat the 2/3 cup cold heavy cream in a small saucepan until it is just about to simmer. You want small bubbles around the edge, not a full boil. Pour the hot cream over the chocolate and let it sit for 2 minutes so the chocolate softens. Stir slowly from the center outward until the ganache becomes glossy and smooth. If a few chocolate pieces remain, keep stirring gently until they melt. The mixture should pour easily but still feel rich and thick.

5-Fifth Step: Add the ganache and chill Pour the ganache over the pudding layer. Tilt the pan gently or use an offset spatula to spread it into an even layer. Be careful not to press too hard, or the filling underneath may shift. After that, place the bars in the refrigerator for at least 4 hours, or until they are fully set. If you have more time, chill them overnight for the best texture and cleanest slices. The longer chill helps the layers stay distinct when you cut into them.

6-Final Step: Slice and serve When the bars are firm, use a sharp knife to cut them into squares. For the neatest slices, wipe the knife clean between cuts. Serve the bars cold so the layers stay in place and the chocolate topping stays smooth.