Bring a pot of salted water to a boil. Add potatoes and boil until you can easily pierce them with a fork (20-25 minutes).

Strain potatoes and let them sit for about 5 minutes. Then, place them on a flat surface and smash them with a potato masher or serving fork to desired thickness.

In a bowl, mix together the butter, olive oil, and garlic. Brush this mixture over the smashed potatoes. Salt and pepper to taste.

Oven method: Preheat oven to 425 F. Place potatoes on a parchment paper lined baking sheet. Bake until golden and crispy, about 25-30 minutes.

Air fryer method: Preheat air fryer to 400 F. Place potatoes in a single layer in air fryer. Cook until golden and crispy, about 10-15 minutes.

Remove potatoes from heat, and top with chimichurri or serve on the side.