Directions

1. Heat oven to 160C/140C fan/gas 3. Put the duck legs in a flameproof casserole set over a medium heat. Brown all over, then remove from the casserole and set aside. Pour off all but 1 tbsp of the fat, leave more fat in the pan if you are doubling or tripling (save the drained fat for your Christmas roasties). Add the carrots and onion to the casserole and cook for 5-10 mins or until starting to caramelise. Stir in the flour and cook for 1 min more. Return the duck along with the remaining ingredients. Bring to a simmer, then cover with a lid and put in the oven for 2 hrs.
2. Meanwhile, prepare the gratin. Put the milk, cream, garlic and rosemary in a pan set over a low heat. Bring to a gentle simmer for 5 mins, then remove from the heat and leave to infuse for 30 mins. Grease 2 ramekins (about 8cm diameter, 5cm deep). Arrange the celeriac and potato slices in the ramekins, seasoning the layers as you go. Remove the garlic and rosemary from the milk, pour over the veg, then dot with butter. Cover tightly with foil and bake with the duck for 1 1/2 hrs.
3. Once cooked, remove the duck and gratins from the oven.To freeze the duck, cool, then pack into a freezer container, pushing the duck under the sauce. If it doesn't cover it, lay cling film on top. Use within 2 months. Thaw in the fridge, then reheat in the casserole and complete from Step 4. Increase oven to 220C/200C fan/gas 7. Put a heavy can on top of each foil-wrapped gratin and stand for 15-20 mins, or chill like this until needed. Once pressed, turn the gratins out onto a baking tray, sprinkle with a little Parmesan and bake for 20 mins until golden.
4. Meanwhile, remove the duck legs from the casserole, strain the cooking liquid into a clean pan and bring to a rapid boil. Reduce the sauce by half until thickened and glossy. Add the duck legs and heat through. Put a duck leg on each plate with a little sauce spooned over the top. Serve with the gratins and seasonal veg.