Make the chimichurri: in a sauté pan on medium heat add kale, leek and a tablespoons of olive oil. Stir continuously, cooking down until leek has caramelized and kale is wilted. Remove mixture from pan and roughly chop again. Transfer to bowl, top with remaining olive oil and season with salt, pepper and red pepper flakes. Stir and as fresh squeezed lemon juice, adding about a teaspoon at a time until desired flavor is reached. Set aside.
Make the potatoes: Preheat oven to 450F. Line a baking sheet with foil and set aside.
In a large bowl combine potatoes, garlic, olive oil , salt and pepper. Toss and massage oil into potatoes until they are completely coated. Transfer to baking sheet and roast for 20-25 minutes, until cooked through and golden.
Remove potatoes from oven and top with half of Leek and Kale Chimichurri. Serve potatoes fresh from the oven with remaining chimichurri.