(This step can be done up to a week ahead of time.)First, make the roasted garlic compound butter by mashing together ¼-cup of softened butter with 10-15 roasted garlic cloves. Roll in plastic wrap and refrigerate until solid. (For more detailed instructions, visit our roasted garlic compound butter recipe.)
Preheat oven to 450°F | 232°C.Line a baking sheet with parchment paper or a silicone mat.We think the potatoes ultimately turn out crispier when using parchment, and even crispier if you use a bare, well-oiled heavy baking sheet.
Place the potatoes in a medium saucepan and add enough water to cover the tops plus about half an inch. Place the saucepan over medium high heat and bring to a boil.Once the potatoes are boiling, add a generous pinch of salt to the water, reduce heat, cover and simmer until potatoes are tender; about 15 minutes. Remove from heat.
Drain the potatoes into a colander and allow them to cool and steam dry for 5-10 minutes.
Place the potatoes in a medium bowl (or just reuse the dry, drained saucepan) and toss with 2 tablespoons of olive oil. Season with a sprinkling of kosher salt.
Arrange the potatoes evenly on the prepared baking sheet.Using a potato masher, hamburger press, or the bottom of a Mason jar, carefully flatten the potatoes until they are about a half to three-quarters of an inch thick, keeping them in one piece if possible.
Drizzle the smashed potatoes with a little more olive oil, and then place a ⅛-inch slice of the Roasted Garlic Compound Butter on the top.
Place the prepared potatoes into the preheated oven and bake for 18-20 minutes, or until golden brown and crisp.Remove from the oven and season with another couple turns of the pepper mill and a sprinkling of kosher salt to taste.
Roasted garlic is one of the most versatile cooking ingredients you can have in your kitchen. It keeps for weeks in the fridge, and can be frozen for up to a year.