Prepare the pudding mixture - In a large bowl, combine the white chocolate pudding mix with 2 cups of cold 2% milk. Add 2-3 drops of neon green gel food coloring and 1-2 drops of regular green food coloring to achieve a vibrant Grinch-green color. Beat the mixture until it thickens and forms soft peaks, about 2 minutes with an electric mixer or 5 minutes by hand.

Fill the crust - Carefully scoop the green pudding mixture into the prepared Oreo pie crust. Use a spatula to spread the filling evenly, ensuring a smooth, level surface that reaches all the way to the edges of the crust.

Refrigerate the pie - Place the pie in the refrigerator and allow it to chill for at least 3 hours. This cooling time is essential for the pudding to set properly and reach the perfect consistency.

Add the topping - Once the pie has set, remove it from the refrigerator. Spread the thawed Cool-Whip evenly over the top of the pie using a spatula, creating a smooth, white layer that resembles snow.

Decorate - Sprinkle the green sanding sugar across the Cool-Whip layer to create a sparkly effect. Scatter the mini red heart sprinkles over the top, distributing them evenly across the pie's surface.

Serve - Cut the pie into slices and place a single large red heart sprinkle on each slice just before serving, representing the Grinch's growing heart.