For roast chicken, preheat oven to 180C. Rinse chicken inside and out and pat dry with absorbent paper. Season to taste inside and out, place in a roasting pan, stuff cavity with thyme and garlic and drizzle skin with oil. Roast until chicken is golden and cooked through (1-1¼ hours).
Meanwhile, cook celeriac in a saucepan of salted boiling water until tender (3-5 minutes). Drain well, then transfer to a large bowl.
Heat oil in a small frying pan over medium heat, add walnuts and stir occasionally until golden (2-4 minutes). Drain, cool and add to celeriac with grapes, celery and shallot.
Coarsely shred chicken (discard skin, bones and sinew) and add to bowl. Add aïoli, lemon juice to taste and mustard, season to taste and toss to combine. Scatter with celery leaves and serve with crusty baguette.
This recipe is from the May 2012 issue of Australian Gourmet Traveller.