Adapted from: Bon Appetit
1/2 cup mayonnaise
1 tablespoon extra virgin olive oil
2 garlic cloves, pressed
2 teaspoons tomato paste
1/8 teaspoon smoked paprika
Pinch of cayenne pepper
1 1/2 pounds unpeeled potatoes, scrubbed, cut into 1" cubes
1/4 cup whole milk
2 tablespoons (1/4 stick) unsalted butter
1 teaspoon coarse kosher salt, divided
3 1/2 tablespoons extra-virgin olive oil, divided
1/2 cup chopped shallots
1 large garlic clove, finely chopped
1/2 pound kale, center rib and stem cut from each leaf, leaves coursely chopped
1 tablespoon chopped fresh thyme
1/8 teaspoon ground nutmeg
Whisk all ingredients in medium bowl. Season rouille to taste with salt and freshly ground black pepper. (DO AHEAD: Can be made one day ahead. Cover and chill.)
Cook potatoes in large saucepan of boiling salted water until tender, about 25 minutes. Drain; return potatoes to same saucepan. Add milk and butter. Mash potatoes (with peel) until smooth. Season with 1/2 teaspoon course salt and 1/2 teaspoon pepper. Transfer 3 cups mashed potatoes to large bowl and cool. (Reserve remaining potatoes for another use.)
Heat 1 1/2 tablespoons oil in large deep skillet over medium heat. Add shallots and garlic. Saute until shallots soften, about four minutes. Increase heat to medium high. Add kale and thyme. Toss until kale wilts, about five minutes. Add kale mixture, 1/2 teaspoon coarse salt, 1/2 teaspoon pepper, and nutmeg to potatoes; blend. Cool potato mixture 30 minutes.
Shape potato mixture by 1/4 cupfuls into 1/2" thick patties. Arrange on rimmed baking sheet. (DO AHEAD: Can be made up to 2 hours ahead. Let stand at room temperature.)
Heat 2 tablespoons oil in large nonstick skillet over medium-high heat. Add cakes and cook, without moving, until cakes are brown and crispy on bottom, 3 to 4 minutes. Carefully turn cakes over. Cook until brown on bottom, 2 to 3 minutes longer. Transfer to plates. Top each cake with dollop of rouille.
Yields 12 cakes.