winter gratin with cheesy leek and rosemary cream
potato bake went to Europe and came back calling herself a gratin
ingredients
1-2 tbsp unsalted butter
1 large leek, white and pale green parts only, finely sliced
2 garlic cloves, finely grated
2-3 tsp fresh rosemary, very finely chopped, plus extra to serve
500ml thickened cream
100g parmesan, finely grated
150g vintage cheddar, grated
3 medium sweet potatoes, peeled
1 butternut pumpkin, peeled, halved and seeds removed
1-1.2kg brushed potatoes, scrubbed or peeled
Sea salt
Freshly cracked black pepper
method
Preheat the oven to 180°C fan-forced. Generously butter a 33 × 23cm baking dish.
Melt 1 tablespoon butter in a frying pan over medium-low heat. Add the leek with a pinch of salt and cook for 8–10 minutes, stirring occasionally, until very soft and sweet but not browned.
Add the garlic and 2 teaspoons rosemary and cook for another 60 seconds, just until fragrant. Pour in the cream and bring to a gentle simmer. Remove from the heat and stir through 50g parmesan. Taste and season with black pepper and a little salt if needed.
Using a mandoline or very sharp knife, slice the brushed potatoes about 2mm thick, the sweet potatoes 2–3mm thick and the pumpkin 3–4mm thick. Keeping the pumpkin slightly thicker will help everything cook at roughly the same rate. Don’t rinse the potatoes. Their starch will help thicken the cream as the gratin cooks.
Season the sliced vegetables with salt and pepper. Arrange them upright in the prepared dish, alternating small stacks of brushed potato, sweet potato and pumpkin. Keep going until the dish is generously filled, with the slices sitting on a slight angle and packed snugly together. You may not need every piece of vegetable.
Slowly pour the warm leek and rosemary cream over the vegetables. Use a small knife or your fingers to gently separate the slices here and there, allowing the cream and softened leek to work their way down into the gratin. The cream doesn’t need to cover the vegetables. You want it to sit roughly one-third to halfway up the sides.
Cover tightly with foil or a lid and bake for 55–65 minutes. Check by inserting a thin knife into one of the brushed potato slices. The potato is your guide here. It should be tender with very little resistance. If it’s still firm, cover and return to the oven for another 10 minutes before checking again.
Increase the oven to 200°C fan-forced. Remove the foil and scatter over the vintage cheddar and remaining 50g parmesan. Return to the oven, uncovered, for 20–25 minutes, until the potatoes are completely tender, the cream is bubbling around the edges and the cheese is deeply golden.
If you want a little more colour, finish under the grill for 2–3 minutes, keeping a close eye on it.
Rest for 10–15 minutes before serving. Finish with a little finely chopped rosemary and freshly cracked black pepper.
Serves 8–10 hungry people
