How to make sweet potato rostis with mushrooms and crispy sage

Christmas isn’t the time to convince your friend they’re not lactose intolerant, says Julia Platt Leonard. Find out who needs what and prep vegan side dishes like this

A fritter alright: no neutral flavours in this Swiss dish (Photos Julia Platt Leonard)

Planning and cooking Christmas dinner is not for the faint of heart. It’s a logistical exercise as much as a cooking one. Add in guests with dietary restrictions and things can get even more complicated. But it doesn’t have to be.

1. Don’t panic. Many dishes can be adapted easily. Making your prize brussels sprouts with toasted walnuts in brown butter, but you’ve got a vegan guest? Sauté them in olive oil instead, and finish them off with a drizzle of walnut oil. Gluten-free guest? Make your stuffing with cornbread instead. And remember that every guest doesn’t have to eat every dish.

2. Full disclosure. Ask your guests if they have dietary restrictions, and listen to them. This is not the time to convince your best friend she’s not really lactose intolerant.

3. The main event. If you’re serving turkey, goose, ham or another meat for Christmas then have a veggie option for your vegan or vegetarian friends. Christmas is about abundance, and if they’re only eating sides then they’re missing out. I’d go for a vegan dish because then you’ve got all your bases covered.

This sweet potato rosti dish is perfect for vegetarians and vegans. You can sauté the mushrooms ahead of time and warm them before serving. If you’re really pushed for time, prepare the rostis and reheat them in a hot oven to crisp them up.

Make sure you don’t scrimp on the lemon juice and lemon zest – the sweet potatoes and mushrooms are both rich, and you need some acid to give the dish a lift. The fried sage leaves aren’t essential but they add a lovely crunch and woody flavour.

Note: use the same frying pan to cook the sage leaves, then sauté the mushrooms and finally make the rostis in order to cut down on clean-up.

(Julia Platt Leonard)

Sweet potato rostis with mushrooms and crispy sage

Makes about 12-15 rostis

1 medium sweet potato, about 400g​
1 lemon
Small bunch of sage leaves
Small bunch of chives, about 5g, chopped
500 mixed mushrooms, either shiitake, brown button, enoki, oyster or chanterelle
Olive oil
Salt and pepper

Wash and thoroughly dry about 20 sage leaves. Heat a few tablespoons of olive oil in a frying pan and add the sage. It will sputter as the leaves fry. Using a pair of tongs, gently turn them, then remove from the oil when crisp and place on a plate lined with a piece of towel paper. Leave any oil in the pan and remove from the heat while you prepare the mushrooms.

With a piece of moist towel paper, wipe away any dirt from the mushroom. Remove the stems from brown button and shiitake mushrooms and gently tear them into quarters or eighths, depending on the size. Place the pan back on the heat. Add more olive oil to the pan so you have a couple of tablespoons in total. Add the button and shiitake mushrooms, add a sprinkle of salt, toss to coat in the oil and cover with a lid.

Let the mushroom cook for a few minutes then remove the top. Add the chanterelles, if using, and then the oyster mushrooms. Remove from the heat and place the mushrooms in a bowl.

Zest the lemon and place in a mixing bowl, along with the chopped chives. Peel the sweet potato and coarsely grate into the bowl. Mix thoroughly and season generously with salt and pepper. Wipe clean the frying pan you used for the mushrooms and add a tablespoon or two of oil. Place a dollop of the sweet potato mixture in the pan, flatten with the back of a spatula. Add more dollops but don’t overcrowd the pan.

When the rostis begin to crisp up along the edges, turn them over and cook on the other side. They should be nicely browned and crisp. Remove and place in a warm oven while you’re making the rest of them. Top up the oil as needed.

When you’re ready to serve, wipe clean the frying pan and add back in the mushrooms to warm. Juice half of the lemon and add to the mushrooms. Trim the woody end of the enoki mushrooms (if using) and add to the pan. Stir briefly and remove from the heat.

Place the rostis on a serving plate or platter, top with the mushrooms and a crispy sage leaf for each one.

@Juliapleonard