Add 3 cloves of smashed garlic, a few large pinches of salt and potatoes to a large pot and cover with cold water. Bring to a boil over high heat and cook until potatoes are just tender, about 10 minutes. Drain potatoes and discard the garlic. Transfer the potatoes to a sheet tray lined with a clean dish towel to dry slightly.
Add enough oil to coat the bottom of a large skillet and heat over medium heat. Add the onion and cook, stirring, until just translucent, about 5 minutes. Add the crushed red pepper and the remaining 2 cloves garlic and cook, stirring, until soft and tender, about 3 minutes. Increase the heat to medium-high and add the cooked potatoes. Cook, stirring frequently, until the potatoes start to get crispy and golden brown on all sides, about 5 minutes. (If the potatoes get too dry, add the chicken stock.) Remove from the heat and stir in the chives.