Add potatoes to a large pot and cover with water. Add 1 teaspoon salt and bring to a boil for 15 minutes, or until potatoes are tender.

In a food processor, place basil, garlic, pine nuts and Parmesan. Add oil and pulse until mixed then season with salt and pepper, to taste.

In a small saucepot over low heat, heat milk and butter until butter is melted and milk is steaming.

Once potatoes are cooked, strain and transfer to a medium mixing bowl.

Using a potato masher, smash potatoes with milk and butter mixture then season with salt and pepper, to taste. Stir in pesto mixture.