Root Vegetable Pot Pie

4 tablespoons unsalted butter

2 tablespoons extra-virgin olive oil

1 onion, halved and thinly sliced

1 leek, halved lengthwise and thinly sliced crosswise

3 garlic cloves, sliced

Kosher salt

Freshly ground black pepper

1kg mixed root vegetables, such as carrots, beets, and sweet potato, cut into 1-inch pieces

1 tablespoon chopped thyme

1/4 cup all-purpose flour

2 cups chicken or vegetable broth

1/2 cup heavy cream

1 teaspoon smoked paprika

1 400-450g sheet puff pastry

1 large egg beaten with 1 teaspoon water to make an egg wash

1 cup frozen peas, thawed slightly

1/2 cup finely chopped parsley

Preheat the oven to 200°C. In a large enamelled cast-iron casserole over medium heat, melt the butter in the olive oil. Add the onion, leek, garlic and a generous pinch of salt and pepper. Cook, stirring occasionally, until softened and just starting to brown, about 8 minutes. Add the root vegetables, thyme, and a generous pinch each of salt and pepper. Cook, stirring occasionally, until the vegetables start to soften off the edges, 8 to 10 minutes.

Sprinkle the vegetable mixture with the flour and cook, stirring, until the mixture is coated and starts to form a film on the bottom of the casserole, 1 to 2 minutes. Gradually add the broth and cook over medium-high heat, scraping up any browned bits from the bottom and side of the casserole, until thickened about 2 minutes. Stir in the heavy cream, paprika and a pinch each of salt and pepper.

Invert the lid of the casserole onto the work surface so that it is standing on the handle. From a large sheet of baking paper, cut out a round the same size as the lid.

If necessary, on a lightly floured work surface, roll out the puff pastry so it's just lightly larger than the lid of the casserole. Using the baking paper round as a guide, cut the pastry into a circle; chill the pastry if too warm. Flip the pastry onto the baking paper round, then brush with the egg wash and sprinkle with salt and pepper. Slide the pastry and baking paper onto the inverted lid, then set the inverted lid with the pastry right onto the casserole, covering it.

Bake in the lower third of the oven for about 30 minutes, until the pastry is puffed and golden. Remove from the oven. Uncover the casserole and stir the peas and parsley into the filling. Slide the pastry on top of the filling and serve.