Cook potatoes: Clean the potatoes well and place them into a pot. Add water, bring to a boil and cook the potatoes for about 15-20 minutes or until fork-tender. The exact cooking time depends on their size, so check if they are cooked through before draining them.
Preheat oven: In the meantime, preheat the oven to 200 degrees Celsius/ 400 degrees Fahrenheit.
Drain the potatoes well and leave them to stand in the colander for about 5 minutes so that most of the water on their surface will evaporate.
Combine: Pour the olive oil into a small bowl. Add the smashed or grated garlic and the chopped rosemary. Mix well.
Smash potatoes: Grease a baking tray with the extra olive oil. Place the potatoes on the baking tray and crush them carefully and only lightly with a fork; they should not be pressed flat but still, have plenty of ridges after you've crushed them.
Bake: Drizzle with the olive oil and garlic mixture evenly, use a teaspoon for that purpose. Sprinkle with salt and pepper and bake for about 20 minutes or until golden and crispy. Increase the baking time slightly if the potatoes are not crispy enough after 20 minutes.
Serve: Take out of the oven, sprinkle again with some coarse salt and pepper and serve immediately as suggested above.