The leeks are the star of this recipe: Cut in thin julienne strips and cooked for a long time on high heat, they become crispy and intensely flavorful. You can substitute carrots for the potatoes, or use both.
Heat the oven to 425.
Carefully wash 1 large or 2 medium Leeks: Cut off the greens and discard, then cut the shanks in half lengthwise and then rinse well to remove all the grit between the layers.
Cut the halved leeks in 2 inch lengths. Slice each one lengthwise into matchsticks.
Place the leeks in a cast iron skillet with 2 T. olive oil, 1/2 t. salt and generously amounts of pepper. Toss them to combine with your hands or a tongs.
Dice 1 lb. of Potatoes or cut into “fries”. Toss them in a bowl with 1 T. olive oil, 1 T. fresh rosemary leaves, and salt. Arrange the potatoes on top of the leeks. It’s important not to mix the two vegetables together initially, as the potatoes will help keep the leeks moist while they cook.
Roast the vegetables in the oven for 25 minutes, then start checking them. The leeks should soften and brown. Eventually they will start to turn dark brown. At this point, stir the pan a few times to toss them with the potatoes.
Continue roasting until the potatoes are nicely brown and the leeks are crispy. Take care not to burn them, but you want to almost burn them.