Preheat your oven to 400°F (200°C). Prepare the purple potatoes and red onion by washing and slicing them into even pieces. Carve white button mushrooms into skull shapes.

Spread the potatoes, onions, and garlic on a greased baking sheet. Drizzle with vegetable oil, season with sea salt and pepper, and roast for about 30 minutes until tender and golden.

In a large pot, bring garlic broth to a boil, then reduce heat to simmer.

Transfer the roasted vegetables to the simmering broth and blend until smooth with an immersion blender.

Stir in heavy cream and mozzarella cheese until melted. Adjust coloring if desired and season to taste.

Simmer on low heat for 15 to 20 minutes, stirring occasionally until thickened.

Ladle soup into bowls and garnish with skull mushrooms, microgreens, and piped mascarpone designs.