1.Preheat the oven to 200°C (180°C fan-forced).
2.Bring ⅔ cup (160ml) water to the boil in a small saucepan, add quinoa. Reduce heat; cook, covered, for 15 minutes or until tender. Cool.
3.Scoop flesh from zucchini using a strong spoon, leaving a 5mm border. Reserve zucchini flesh. Trim leek, if needed, to fit inside zucchini.
4.Scoop seeds from pumpkin; discard. Scoop flesh from pumpkin, making a cavity large enough to fit zucchini. Reserve pumpkin flesh. Trim the zucchini, if needed, to fit inside pumpkin. Prick the insides of zucchini and pumpkin with a fork. Process reserved zucchini and pumpkin flesh with onion and garlic until chopped finely.
5.Heat 2 tablespoons of the oil in a large frying pan over medium heat. Add processed vegetables, thyme and quinoa; season. Cook, stirring, for 5 minutes or until tender. Cool.
6.Meanwhile, to make stuffing, combine ground linseed and the hot water in a medium bowl; stand for 10 minutes. Combine linseed mixture with quinoa mixture, cranberries and hazelnut meal.
7.Press some of the stuffing into zucchini cavities. Press leek into one half of the zucchini; cover with the other half. Press remaining stuffing into pumpkin cavities. Place stuffed zucchini in one pumpkin half; cover with the other half. Secure pumpkin together with kitchen string. Brush with remaining oil; season. Wrap in foil; place in a roasting pan.
8.Roast for 1½ hours. Uncover and roast for a further 30 minutes or until outside is browned and vegetables are tender. Cover loosely with foil; stand for 30 minutes. Serve.
Serve with roast potatoes and vegan gravy.
Shop for the leek, zucchini and pumpkin at the same time, so you can check that they will fit inside each other.Note