For this gratin, a white sauce is required. Making a white sauce can sometimes be slightly intimidating – but have no fear. When making the sauce, keep whisking as you add milk slowly and allow the white sauce to cook and thicken slightly between milk additions. You want it to end up like thick cream that does not dollop, but still runs smoothly. It also benefits from a healthy dose of seasoning with both salt and pepper.

Ingredients: 1 Leek, 250g butternut squash, 100g cauliflower,  sprig of thyme, 1 stem of rosemary, 50g rocket.

Larder: 25g butter, 2 heaped tbsp flour, 450ml milk, 75g cheddar cheese, 40g breadcrumbs (1 piece of bread), juice and zest of 1 lemon.

Instructions:

• Preheat the oven to 200 degrees C.
• Slice the leek in half lengthways and then slice the lengths into chunks. Peel and slice the squash into small chunks. Break the cauliflower into small florets. Place all together in a small casserole dish or tin. Drizzle with oil and season. Place in the oven to roast.
• Meanwhile, make a white sauce: Melt approx 25g butter and when it begins to foam, add 2 tbsp flour and stir into a paste. Cook over a low heat for a minute or so and then add about 100ml of milk, stirring constantly. Keep stirring and adding milk slowly so that it thickens to the consistency of double cream. If it becomes too thick, add a dash more milk. Stir in grated cheese and the thyme leaves.
• While the white sauce is thickening, grate a slice of bread using a fine grater to make rough breadcrumbs. Heat a tbsp oil in a small frying pan, add the rosemary leaves and grate in the zest of a lemon and fry for about 30 seconds. Then add the breadcrumbs and fry for a further 30 to 60 seconds until browned or slightly crispy. Remove the veg from the oven, pour over the white sauce and sprinkle with the lemon, rosemary breadcrumbs and return to the oven.
• Remove when bubbling and crispy on top. Serve with rocket and a squeeze of lemon.