Roast chicken with mixed mushroom stuffing

Name: Roast chicken with mixed mushroom stuffing
Ingredients: olive oil; 1 onion, peeled and finely chopped; 4 cloves of garlic, peeled and finely sliced; 500g mixed, interesting mushrooms (such as shiitake, oyster, chestnut etc) cleaned – large ones chopped up, small ones ripped up; a bunch of fresh thyme; 1 lemon; sea salt and freshly ground black pepper; a large handful of pine nuts; 2 large handfuls of fresh white breadcrumbs; 1 free-range egg, beaten; 1 x whole higher welfare chicken (approx. 1.5kg)