Directions
Melt the butter (or heat the olive oil) in a saucepan over a medium heat. Add the leeks and a pinch of salt and sauté, stirring occasionally, until the leeks have softened and are beginning to color (about 10 minutes).
While the leeks are cooking, wash and peel the sweet potato and parsnips. Grate on the coarse holes of a box grater, and place in a large bowl (if you have no patience for hand-grating, you can use the shredding disk on a food processor, but place about ¼ of the mixture back in the bowl of the processor with the regular blade and pulse a few times). Add the salt, pepper, nutmeg, feta, egg and matzo meal. Stir to combine. Mix in the cooked leeks.
Pour the canola oil to a depth of 1/2-inch in a frying pan—you can use the pan used for the leeks, and additional pans if you’d like to make quick work of it. Heat the oil over a medium flame until hot—if you drop in a shred of the latke mixture, it should bubble vigorously. Shape about 3 tablespoons of the latke mixture into a round shape (I like to pack a 1/4 cup measure mostly full), and place in the oil. Flatten slightly to form a small pancake. Repeat as many times as your pan space allows. Cook the latkes until well-browned, 5 to 7 minutes, then flip and brown the other side. These latkes are more delicate than standard potato pancakes (especially when warm), so be delicate. When the second side has cooked, place on a plate lined with brown paper, stacking as needed. If you want to be extra-good, now and then strain out any rogue bits that have floated into the oil before they burn (or leave them in, for a taste closer to what grandma would have made). Serve. Or...
If you’re not serving at once, layer the cooled latkes in a sealed container with parchment between the layers, and freeze. To serve, preheat the oven to 375° F. Place the latkes on a cookie sheet (you can place them on a rack on top of a cookie sheet for a crisper result, but usually the sheet is fine for me), and cook until they have colored a bit more and are heated through
