To assemble, place the carrots, parsnip, swede and leeks in an oven proof dish, break the stilton into small pieces and stir it in. Using the back of a spoon, spread the crème fraiche over the top. Slice the potatoes about 5mm thickness and place in a single layer over the top. Finally, sprinkle the breadcrumbs evenly over the potato. Place in the oven for 25 minutes. If cooking straight from the fridge, you may need 30 minutes.