Preheat the oven to 180 degrees C.
Wash green leaves of the leek and chop it finely with broccoli stalks. Leave broccoli florets for later. Place them vegetables in a large casserole pot in a medium heat with butter, add thyme leaves and cook gently for around 15 minutes, until the vegetables soften. Just remember to stir it regularly.
Add the gluten free flour, mixing it in. Then gradually ad the milk and cook it for around 10 minutes, mixing, or until the mixture thickens. In the meantime cook the pasta in slightly salted water, boiling it for 5 minutes and drain the water from it.
Grate all Parmesan and most of the Cheddar cheese into the veg and milk sauce and stir in well. Pour it into the liquidiser, add spinach and blend until smooth. If it doesn't fit into your blender, then do it in batches.
Season the green sauce with salt and pepper and mix it well with pasta and broccoli florets. If the sauce appears too thick, you can add a splash of lactose free milk.
Place all pasta with sauce in an oven proof dish (you can make individual ones), sprinkle leftover cheddar cheese and some flaked almonds.
Bake it for around 30 minutes, until the top will be golden and the sauce will be bubbling away in the sides.