How to Make It
Preheat the oven to 375°. Prick the potatoes and bake for 50 minutes, or until tender. When cool enough to handle, scoop the flesh into a bowl and coarsely mash; let cool slightly. Lower the oven temperature to 250°.
In a small skillet, toast the cumin seeds over moderate heat, shaking the pan occasionally, until fragrant, about 2 minutes; transfer to a plate to cool.
In a large bowl, mix the eggs with the chives, cornstarch, baking powder, ground cumin, toasted cumin seeds and salt. Add the potatoes and mash just until chunky and blended. Divide the potato mixture into 16 portions, then form into 2 1/2-inch patties.
In a large nonstick skillet, melt 1 tablespoon of the butter in 1 tablespoon of the olive oil. Add 8 patties to the skillet and cook over moderate heat, turning once, until crisp and golden, about 5 minutes per side. Transfer to the oven and keep warm. Repeat with the remaining patties. Transfer the hot potato cakes to a platter and serve.