Preheat the oven to 200C/gas 6 and generously butter a gratin dish – about 26cm in length.
Put the lemon juice into a large bowl and add two or three times as much water. Peel all the roots and cut into batons about 4 x 1cm, dropping them straight into the lemony water to stop them discolouring.
When all the roots have been prepared, drain them and put them in a saucepan with the vegetable stock and wine. Bring to a simmer and cook for about 5 minutes - until the roots are tender but still with a bit of bite. Drain, reserving the stock, and set aside. Return the stock to the pan and simmer until reduced by half.
Meanwhile, mash the soft butter and flour together with a fork. When the stock has reduced by half, keep it simmering and start sprinkling in the flour paste, in little nuggets, whisking all the time. Keep whisking until the sauce thickens to the consistency of single cream. Add the double cream and remove from the heat.
Lay the root batons in the gratin dish. Pour over the thickened stock. Combine the grated cheeses with the breadcrumbs and sprinkle over the top. Bake for 15-20 minutes, until golden.
I rated this recipe 4.5 stars, but the 'star meter'showed it as 1.5 !!! Dont be mislead, its definately a 4.5 !!!
I made this with parsnips....and it was fabulous!!!! A great way to vary a winter veg.