Cook 1 1/2 pounds small red potatoes in salted boiling water until tender, 15 to 20 minutes. Reserve 1 cup cooking water, then drain. In the same pot, cook 2 chopped shallots and 2 chopped garlic cloves in olive oil over medium-high heat until softened, 2 minutes. Add 4 cups chopped kale and 1/2 cup cooking water; cook 5 minutes. Add 1/2 cup milk and bring to a simmer. Off the heat, add the potatoes, 3 tablespoons olive oil and some chopped parsley. Mash, adding more cooking water if needed. Season with salt and pepper.