Begin by preheating your oven to 200C/390F.

Trim the tops off the garlic bulbs to reveal the cloves, then drizzle them with a bit of olive oil and wrap each bulb in foil.

Carefully slice the potatoes into very thin cuts, about 1/16" to ⅛" thick, making sure not to cut all the way through so they remain whole.

In a large mixing bowl, combine the sliced potatoes with 3 tablespoons of olive oil, ½ teaspoon of salt, and ¼ teaspoon of black pepper. Toss them well to ensure they are evenly coated.

Arrange the potatoes cut-side-up on a baking tray. Use a brush to gather any remaining oil from the bowl and apply it over the tops of the potatoes.

Place the wrapped garlic bulbs on the tray alongside the potatoes and roast everything in the oven for 30 minutes.

After 30 minutes, take the tray out and brush the potatoes with any excess oil that has collected in the tray. If the garlic appears to be browning too quickly, reduce the oven temperature to 180C/350F.

Return the tray to the oven and roast for an additional 15 to 20 minutes, or until the potatoes are a deep golden color and crispy, and the garlic is soft, light golden, and sticky.

Once done, squeeze the roasted garlic into a small bowl and mix it with the butter, parsley, and a pinch of salt and pepper to taste. Be cautious as the garlic may be hot; you might want to use a kitchen towel for protection.

Stir the mixture well to combine, then generously spread it over the hot potatoes.