Preheat the oven to 375°F (190°C).
In a medium bowl, combine 1 cup all-purpose flour, ½ cup crushed nuts, ¼ cup sugar, and 8 tablespoons salted butter (melted). Stir until the mixture is evenly moistened and holds together when pressed.
Press the mixture firmly and evenly into the bottom of a 9×13-inch baking dish to form the crust.
Bake the crust for 10 minutes. Remove from the oven and let the crust cool completely in the pan.
Once the crust is cool, spread the 21 ounces cherry pie filling evenly over the crust.
In a large bowl, beat 8 ounces softened cream cheese with a mixer until light and fluffy. Add 1 cup Cool Whip (from the 8 oz container) and beat until combined. Gradually add 1 cup powdered sugar and beat until the mixture is smooth.
Spread the cream cheese mixture evenly over the cherry layer.
In a separate bowl, whisk together the 6.8 ounces (2 packages) chocolate instant pudding mix and 3 cups milk according to the package instructions until the pudding thickens. (If the package gives a recommended whisking time, follow that.)
Spread the prepared chocolate pudding evenly over the cream cheese layer.
Spread the remaining Cool Whip from the 8 oz container over the pudding layer.
If desired, sprinkle ½ cup chocolate shavings or chocolate jimmies evenly over the top.
Keep the assembled dessert refrigerated until serving.