Boil potatoes: Scrub them, place them in the pot, and cover them with cold water. Add a generous pinch of salt. Bring to a boil, turn the heat down a bit, and cook the potatoes until fork-tender; it will take about 15 minutes, but check.1 ½ lbs small potatoes / 700 g
Drain them well and let them steam for about 5 minutes.
Butter mixture: In the meantime, melt the butter in a small saucepan. Mix it with the grated garlic, finely chopped rosemary, and all the spices.4 tablespoons butter / 60 g + 3 garlic cloves + 1 sprig of rosemary + ½ teaspoon sweet paprika + ¼ teaspoon red chili flakes +
Smash: Generously oil the baking sheet using a pastry brush. Place the potatoes on it and smash them about ½ inch thick (1.3 cm) using a potato masher, a fork, or the bottom of a glass. Don't flatten them completely; they should still be chunky for the best crispy texture.
Brush them with the butter mixture using the same pastry brush.
Bake in the preheated oven for 10 minutes.
Add cheese: Sprinkle them with the grated cheese and bake them for another 8 minutes or so until the cheese is melted.¾ cup sharp Cheddar / 90 g + 1-2 tablespoons chives
Sprinkle them with chives, a bit of flaky sea salt, and freshly ground black pepper, and serve them immediately.
Notes
Potatoes: For best results, use small potatoes, not larger than 2 inches (50 mm) in diameter (about the size of a golf ball). Yellow, red, or fingerling potatoes are great.
Herbs: You can use dried rosemary (about 1 teaspoon) or other dried herbs such as thyme, oregano, Italian seasoning, or herbs de Provence.
Cheese: You can use other good-melting cheeses, such as Gouda, Gruyere, Fontina, Monterey Jack, Colby, or Parmesan. I would not use mozzarella alone; I think it lacks flavor.
Grate the cheese yourself; I don’t recommend using pre-grated cheese; its additives prevent it from melting nicely.