Prepare the Mashed Potatoes:

1. Boil the Potatoes: In a large pot, bring salted water to a boil. Add the cubed potatoes and cook until tender, about 15-20 minutes.
2. Drain and Mash: Drain the potatoes and return them to the pot. Add the sour cream, milk, butter, garlic powder, salt, and pepper. Mash until creamy and smooth.
3. Mix in Cheese and Bacon: Stir in the shredded cheese and crumbled bacon (if using) until well combined.

Assemble the Casserole:

4. Preheat the Oven: Preheat your oven to 350°F (175°C).
5. Transfer to a Baking Dish: Spoon the mashed potato mixture into a greased 9×13-inch baking dish, smoothing the top with a spatula.

Create the Spider Web:

6. Add Mozzarella: Sprinkle the shredded mozzarella cheese evenly over the top of the mashed potatoes.
7. Form the Web: Use a spoon or a piping bag to create a spiral pattern with the mozzarella, starting from the center and working your way outwards. Then, use a knife to create lines radiating from the center to form the spider web design.
8. Bake: Bake in the preheated oven for about 25-30 minutes, or until the cheese is bubbly and golden.

Decorate:

9. Add Olives: Once out of the oven, place sliced black olives at various points on the spider web to resemble spiders.
10. Garnish: Optionally, sprinkle with parsley for a touch of color.