Heat the oven to 180°C (350°F). Halve the potatoes and boil for 10–15 minutes, until a fork slides through easily. Drain well and let the surface moisture evaporate.
Drizzle the olive oil over a baking tray. Scatter half the mozzarella in a thin layer where the potatoes will sit.
Place the potato halves cut-side up on the cheese. Press each one flat with the base of a glass or a broad spoon, keeping each piece together.
Season with salt, paprika, chili powder and garlic powder to taste. Sprinkle the remaining mozzarella over the potatoes.
Bake for about 12 minutes, until the cheese is golden and the edges are crisp. Ovens and potato thickness vary, so use the golden edges as your guide.
For the optional dip, stir the mayonnaise, sriracha, mustard and 1 teaspoon paprika together. Add a splash of water to loosen, then finish with dried parsley. Serve the potatoes hot with the dip.