Preheat your oven to 425°F (220°C) and line a large baking sheet with parchment paper for easy cleanup.
Wash and dry the baby potatoes thoroughly. If some are larger than others, cut them in half so all pieces are roughly the same size for even cooking.
Fill a large pot with water, add ½ teaspoon of baking soda and 1 teaspoon of salt. The baking soda creates a slightly alkaline environment that breaks down the potato surface, leading to more crispiness.
Bring the water to a boil and add the potatoes. Cook for 8-10 minutes until the potatoes are fork-tender but not falling apart—you want them parboiled, not fully cooked.
Drain the potatoes thoroughly in a colander and let them steam dry for about 30 seconds. Give the colander a gentle shake to rough up the edges of the potatoes—these rough edges will crisp up beautifully!
Transfer the potatoes to a large bowl and add olive oil, melted butter, minced garlic, rosemary, salt, and pepper.
Toss gently until all potatoes are evenly coated with the oil and seasoning mixture, being careful not to break them.
Arrange the potatoes in a single layer on your prepared baking sheet, ensuring they’re not touching each other for maximum crispiness.
Roast in the preheated oven for 25-30 minutes, flipping halfway through, until golden brown and audibly crispy when tapped with a utensil.
Sprinkle with fresh parsley and serve immediately for the best texture and flavor experience.