Step 1

Place 3 (3.4-ounce) packages instant vanilla pudding and 1 quart whole milk in a large bowl and whisk until smooth. Add 1 (8-ounce) tub Cool Whip and use a flexible spatula to gently fold together until well combined.

Step 2

Arrange a layer of graham crackers (about 1 sleeve) in 9x13-inch baking dish, breaking the crackers as needed to fit. Spread half of the pudding mixture evenly over the graham crackers. Arrange a second layer of graham crackers on top of the pudding mixture. Spread the remaining pudding mixture over the top. Finish with a third layer of graham crackers.

Step 3

Place 1 cup dark chocolate chips, 3/4 cup heavy cream, 1/4 cup light corn syrup, and 1/8 teaspoon kosher salt in a medium microwave-safe bowl. Microwave on HIGH in 15-second increments, stirring after each increment, until the chocolate is melted and the mixture is completely smooth, about 1 minute total. (Alternatively, heat in a small saucepan on the stovetop over low heat.)

Step 4

Pour the chocolate mixture evenlly over the top layer of graham crackers. Smooth it out with the spatula. Cover the baking dish and refrigerate for at least 8 hours or up to overnight before cutting and serving.