Celeriac and rocket sformato

Method

1. Heat the oven to 200°C/180°C fan/gas 6. Cut three quarters of the celeriac into 1cm thick slices, then into chunky triangles. Chop the remaining celeriac into 1.5cm cubes. Put the triangles on one side of a large baking tray and the cubes on the other side. Toss with oil, salt and pepper, then roast for 25-30 minutes until softened and golden.
2. Meanwhile, melt the butter in a saucepan, then stir in the flour to form a paste. Cook for 1 minute, then remove from the heat and whisk in the milk a little at a time until smooth. Return to the heat, bring to the boil, stirring, then simmer the sauce for 2-3 minutes until thickened. Transfer to a large bowl and set aside to cool completely.
3. Rinse the spinach and 200g of the rocket, then put in a clean saucepan (leave some water clinging to the leaves to help the greens cook). Put the pan on a low heat and gently cook until wilted (3-4 minutes). Drain, squeezing out any moisture, then roughly chop.
4. Once the sauce has cooled, stir in the ricotta, eggs, a generous grating of nutmeg and 75g of the grated hard cheese. Next, gently stir in the roast celeriac triangles and chopped greens. Season with salt and pepper, then pour the mixture into the prepared tin, level the top with a spatula and sprinkle over the remaining 25g hard cheese. Bake for 35-40 minutes until golden and just set. Cool in the tin for 10 minutes, then transfer to a serving plate.
5. Top with the roast celeriac cubes, remaining rocket, chopped tarragon and toasted pine nuts. Drizzle with a little oil and slice to serve.