1. Line the bottom of a 9×13 inch baking dish with a single layer of graham crackers, breaking a few to fully cover the surface.

2. In a large bowl whisk the instant vanilla pudding mix with the cold milk for about 2 minutes until thick and smooth, then stir in the vanilla extract and pinch of salt. Let stand 3 to 5 minutes to finish thickening.

3. Gently fold the thawed whipped topping into the pudding mixture in two or three additions until the filling is light, fluffy, and well combined.

4. Spread half of the vanilla filling evenly over the graham cracker layer in the pan.

5. Add a second full layer of graham crackers over the filling, covering the surface completely.

6. Spread the remaining vanilla filling over the second cracker layer, then top with a final layer of graham crackers to finish the cake structure.

7. Place the chocolate chips in a heatproof bowl. Heat the heavy cream in a small saucepan over medium heat just until steaming and small bubbles form around the edges, then pour the hot cream over the chocolate chips.

8. Add the light corn syrup and butter to the bowl if using, let sit for 2 to 3 minutes, then whisk slowly until the ganache is completely smooth and glossy.

9. Let the ganache cool for 5 to 10 minutes so it slightly thickens but is still pourable, then pour it over the top graham cracker layer and gently spread it to the edges of the pan.

10. Cover the pan tightly with plastic wrap or foil and refrigerate for at least 4 hours or overnight until the crackers soften and the layers are fully set.

11. When ready to serve, slice the Chocolate Eclair Cake into squares with a sharp knife, wiping the blade between cuts for neat pieces, and serve cold from the refrigerator.