1. Prepare the Pan

Line an 8×8‑inch square baking pan with parchment paper, leaving overhangs on two opposite sides (so you can lift out the slab later). Lightly mist the pan and parchment with cooking spray.

2. Make the Crust

• In a food processor, pulse the vanilla wafers and granulated sugar until they become fine crumbs (about 20 seconds).
• Pour in the melted butter and pulse 4–6 times until the crumbs are evenly moistened.
• Alternatively: crush the wafers in a resealable bag using a rolling pin; then stir in sugar and melted butter in a bowl.
• Transfer the wet crumbs to the lined pan, press firmly into an even layer (use the flat bottom of a cup or your hands).
• Freeze this crust for 15 minutes to firm up.

3. Make the Custard Layer

• In a large bowl, whisk together the two pudding mix packets with 2 ½ cups of cold heavy cream. (It will thicken quickly.)
• Spread the pudding mixture over the chilled crust layer in an even layer.
• Chill in the refrigerator for at least 10 minutes. (Use this time to prepare the ganache.)

4. Make the Ganache

• Place the chopped semi‑sweet chocolate into a medium heatproof bowl.
• In a small saucepan, bring the ⅔ cup of heavy cream to a simmer (do not boil).
• Pour the hot cream over the chocolate and let sit for 1 minute.
• Whisk gently until the chocolate is fully melted and the ganache is smooth.
• Let it cool a bit—about 3 minutes for a smooth pour, or 5 minutes if you want to make decorative swoops.

5. Assemble & Chill

• Pour the ganache over the custard layer in an even sheet.
• If desired, use the back of a spoon or knife to create swooping patterns in the chocolate.
• Refrigerate until fully set—at least 2 hours (or overnight for firmer cuts).
• When ready, use the parchment overhangs to lift the slab from the pan.
• Place on a cutting board and slice into 12 or 16 squares. Wipe your knife between cuts for clean edges.